20 easy SAT Systems with nonlinear equations questions
These are the questions most test-takers get right. They are worth practising anyway: on the digital SAT the easy questions in Module 1 are what route you into the harder, higher-scoring Module 2, so dropping one costs more than it looks.
Every question below is a real item from the SAT Climb bank, tagged easy by the same difficulty model the app uses to build your practice. Pick an answer before you open the explanation.
y=x−4y=x2−10
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of y1+y2?
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Why C is right
Substituting y=x−4 into the second equation gives x−4 = x2 - 10, which simplifies to x2 - x−6=0. Factoring yields (x−3)(x+2)=0, so x1 = 3 and x2 = -2. The corresponding y-values are y1 = 3 - 4 = -1 and y2 = -2 - 4 = -6. Therefore y1+y2 = -1 + (-6) = -7.
Why the others are wrong
AThis results from computing x₁ · x₂ = -6 instead of y₁ + y₂.
BThis is one of the intermediate values in the calculation, not the sum of both y-coordinates.
DThis results from incorrectly computing the sum with a sign error.
Question 2Easy
y=−3x+7y=x2+x−5
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of x1+x2?
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Why B is right
Substituting y=−3x+7 into the second equation gives −3x+7 = x2 + x−5, which simplifies to x2 + 4x−12=0. By Vieta's formulas, the sum of the roots is the negative of the coefficient of x divided by the leading coefficient, so x1+x2 = -4.
Why the others are wrong
AThis results from incorrectly taking the positive value of the sum instead of the negative.
CThis is one of the x-coordinates from the factored form or a constant in the problem, not the sum.
DThis is the constant term from one of the equations, not the sum of the x-coordinates.
Question 3Easy
In the xy-plane, the graph of y=(x−1)2 intersects the graph of y=3x+1 at two points.
What is the solution (x, y) with the greater y-value to this system of equations?
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Why B is right
Setting (x−1)2=3x+1 gives x2 - 2x+1=3x+1, which simplifies to x2 - 5x=0. Factoring yields x(x−5)=0, so x=0 or x=5. When x=5, y=3(5) + 1 = 16. The solution with the greater y-value is (5, 16).
Why the others are wrong
AThis results from an arithmetic error in solving the quadratic, obtaining x = 4 instead of x = 5.
CThis includes a sign error when solving x(x - 5) = 0, obtaining x = -5 instead of x = 5.
DThis uses the correct x-value but drops a term when computing y, obtaining 14 instead of 16.
Question 4Easy
y=4xx2+y2=68
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of y1+y2?
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Why D is right
Substituting y=4x into the circle equation gives x2 + (4x)2=68, which simplifies to x2 + 16x2=68 or 17x2=68, so x2 = 4 and x=±2. The corresponding y-values are y1 = 4(2)=8 and y2 = 4(−2)=−8. Therefore y1+y2 = 8+(−8)=0.
Why the others are wrong
AThis represents finding only one y-value instead of computing the sum.
BThis represents the coefficient from the linear equation instead of the sum of y-values.
CThis results from a sign error, possibly adding absolute values instead of the actual y-values.
Question 5Easy
y=x2−3y=x−3
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of y1+y2?
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Why B is right
Substituting y=x−3 into the first equation gives x−3 = x2 - 3, which simplifies to x2 - x=0 or x(x−1)=0. The solutions are x=0 and x=1. The corresponding y-values are y1 = 0 - 3 = -3 and y2 = 1 - 3 = -2. Therefore y1+y2 = -3 + (-2) = -5.
Why the others are wrong
AThis results from incorrectly doubling one of the y-values instead of summing both.
CThis is only one of the two y-coordinates, not their sum.
DThis results from an error in sign when computing the sum.
Question 6Easy
x2+y2=25y=4
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of |x1−x2|?
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Why D is right
Substituting y=4 into x2 + y2 = 25 gives x2 + 16 = 25, so x2 = 9. The solutions are x1 = 3 and x2 = -3. Therefore |x1−x2| = |3 - (-3)| = |6| = 6.
Why the others are wrong
AThis represents finding only one x-value (3) instead of computing the absolute difference between both solutions.
BThis incorrectly uses x² = 9 directly as the answer instead of finding the difference of the actual x-values.
CThis results from computing 3 - (-3) = 6 but then incorrectly applying a negative sign, forgetting absolute value makes the result positive.
Question 7Easy
In the xy-plane, the graph of y=x2−6x+5 intersects the graph of y=−3 at two points.
What is the solution (x, y) with the smaller x-value to this system of equations?
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Why A is right
Setting x2 - 6x+5=−3 gives x2 - 6x+8=0, which factors as (x−2)(x−4)=0. The solutions are x=2 and x=4. The smaller x-value is x=2, giving the point (2, -3).
Why the others are wrong
BThis results from a sign error when solving the quadratic equation, obtaining x = -2 instead of x = 2.
CThis uses the correct x-value but drops the constant term when computing y, obtaining 5 instead of -3.
DThis results from an arithmetic error in factoring, obtaining x = 1 as a factor instead of x = 2.
Question 8Easy
y=x−2x2+y2=100
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of x1⋅x2?
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Why A is right
Substituting y=x−2 into the circle equation gives x2 + (x−2)2=100. Expanding yields x2 + x2 - 4x+4=100, which simplifies to 2x2−4x−96=0 or x2 - 2x−48=0. By Vieta's formulas, the product of the roots is -48.
Why the others are wrong
BThis results from a sign error when applying Vieta's formulas or computing the product.
CThis represents finding only one x-value instead of computing the product of both.
DThis represents the coefficient from the linear term instead of the product of solutions.
Question 9Easy
y=x−1y=x2−7x+11
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of y1+y2?
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Why A is right
Substituting y=x−1 into the second equation gives x−1 = x2 - 7x+11, which simplifies to x2 - 8x+12=0. Using Vieta's formulas, x1+x2 = 8. Since y=x−1, we have y1+y2 = (x1 - 1) + (x2 - 1) = x1+x2 - 2 = 8 - 2 = 6.
CThis represents only one y-coordinate value rather than the sum of both.
DThis results from a sign error in computing the sum.
Question 10Easy
y=x+8y=x2−2x
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of x1⋅x2?
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Why A is right
Substituting y=x+8 into the second equation gives x+8 = x2 - 2x, which simplifies to x2 - 3x−8=0. By Vieta's formulas, the product of the roots is the constant term divided by the leading coefficient, so x1⋅x2 = -8.
Why the others are wrong
BThis results from incorrectly taking the positive value of the product instead of the negative.
CThis is the sum of the x-coordinates (x₁ + x₂ = 3 from Vieta's formulas), not their product.
DThis is one of the x-coordinates from solving the quadratic, not the product of both.
Question 11Easy
In the xy-plane, the graph of y=x2+2x intersects the graph of y=8 at two points.
What is the solution (x, y) with the greater x-value to this system of equations?
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Why C is right
Setting x2 + 2x=8 gives x2 + 2x−8=0, which factors as (x+4)(x−2)=0. The solutions are x=−4 and x=2. The greater x-value is x=2, giving the point (2, 8).
Why the others are wrong
AThis uses the smaller x-value solution x = -4 instead of the greater x-value.
BThis results from an arithmetic error in factoring, obtaining x = 3 as a factor instead of x = 2.
DThis uses the correct x-value but drops a term when computing y, obtaining 6 instead of 8.
Question 12Easy
y=x+6y=x2−36
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of x1+x2?
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Why D is right
Substituting y=x+6 into the second equation gives x+6 = x2 - 36, which simplifies to x2 - x−42=0. Factoring yields (x−7)(x+6)=0, so x=7 or x=−6. Therefore x1+x2 = 7 + (-6) = 1.
Why the others are wrong
AThis represents finding only one x-coordinate instead of computing the sum.
BThis results from a sign error when computing the sum.
CThis represents using only the negative solution or making an error in the sum calculation.
Question 13Easy
y=2x−1y=x2−4x+3
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of x1⋅x2?
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Why D is right
Setting the expressions equal gives 2x−1 = x2 - 4x+3. Rearranging yields x2 - 6x+4=0. By Vieta's formulas, the product of roots is c/a=4/1=4. Alternatively, solving gives x=3±5 and (3+5)(3−5)=9−5=4.
Why the others are wrong
AThis results from confusing the product with the sum of y-coordinates or another calculation error.
BThis results from a sign error when applying Vieta's formulas or rearranging the equation.
CThis results from finding only one solution and using that value as the product.
Question 14Easy
y=5y=x2+2x−20
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of x1⋅x2?
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Why A is right
Substituting y=5 into the second equation gives 5 = x2 + 2x−20, which simplifies to x2 + 2x−25=0. By Vieta's formulas, the product of the roots is the constant term divided by the leading coefficient, so x1⋅x2 = -25.
Why the others are wrong
BThis results from incorrectly taking the absolute value of the product or missing the negative sign.
CThis is the y-value of both solutions, not the product of the x-coordinates.
DThis is the sum of the x-coordinates (x₁ + x₂ = -2 from Vieta's formulas), not their product.
Question 15Easy
In the xy-plane, the graph of y = -2x2+10 intersects the graph of y=2 at two points.
What is the solution (x, y) with the positive x-value to this system of equations?
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Why D is right
Setting −2x2+10=2 gives −2x2=−8, so x2 = 4. Taking the square root yields x=±2. The positive x-value is x=2, giving the point (2,2).
Why the others are wrong
AThis results from an arithmetic error when solving x² = 4, obtaining x = 3 instead of x = 2.
BThis uses the negative x-value solution x = -2 instead of the positive x-value.
CThis uses the correct x-value but incorrectly uses the y-intercept of the parabola instead of y = 2.
Question 16Easy
y=3x+2y=x2−6
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of x1⋅x2?
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Why A is right
Substituting y=3x+2 into the second equation gives 3x+2 = x2 - 6, which simplifies to x2 - 3x−8=0. By Vieta's formulas, the product of the roots is the constant term divided by the leading coefficient, which is -8/1 = -8.
Why the others are wrong
BThis results from computing the sum of the roots instead of the product.
CThis results from a sign error when applying Vieta's formulas or rearranging the equation.
DThis is the x-coordinate of only one solution rather than the product of both.
Question 17Easy
y=x2−4y=2x+5
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of x1+x2?
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Why B is right
Substituting y=2x+5 into the first equation yields 2x+5 = x2 - 4. Rearranging gives x2 - 2x−9=0. By Vieta's formulas, the sum of the roots is the opposite of the coefficient of x divided by the leading coefficient, which is -(-2)/1 = 2.
Why the others are wrong
AThis results from incorrectly applying Vieta's formulas with the wrong sign, treating the sum as -2 instead of 2.
CThis is the x-coordinate of only one solution, not the sum of both x-coordinates.
DThis is the sum of the y-coordinates y₁ + y₂, not the sum of the x-coordinates.
Question 18Easy
y=x+5y=x2−3
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of x1+x2?
Show the answer and explanation
Why B is right
Substituting the first equation into the second gives x+5 = x2 - 3, which simplifies to x2 - x−8=0. By Vieta's formulas, the sum of the roots is the negative of the coefficient of x divided by the coefficient of x2, which is -(-1)/1 = 1.
Why the others are wrong
AThis results from incorrectly taking the sum as -1/1 instead of -(-1)/1.
CThis is the x-coordinate of only one solution, not the sum of both x-coordinates.
DThis is the sum of the y-coordinates, y₁ + y₂, not the sum of the x-coordinates.
Question 19Easy
y=4x+1y=x2+5x−2
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of x1+x2?
Show the answer and explanation
Why B is right
Substituting y=4x+1 into the second equation gives 4x+1 = x2 + 5x−2, which simplifies to x2 + x−3=0. By Vieta's formulas, the sum of the roots is -1/1 = -1.
Why the others are wrong
AThis results from a sign error when applying Vieta's formulas or when rearranging the equation.
CThis is the x-coordinate of only one solution rather than the sum of both.
DThis results from adding the y-coordinates instead of the x-coordinates or from reading the coefficient incorrectly.
Question 20Easy
y=x2+3x−10y=x+2
The system of equations above has solutions (x1,y1) and (x2,y2). What is the value of x1x2?
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Why A is right
Substituting y=x+2 into the first equation yields x+2 = x2 + 3x−10. Rearranging gives x2 + 2x−12=0. By Vieta's formulas, the product of the roots is the constant term divided by the leading coefficient, which is -12/1 = -12.
Why the others are wrong
BThis is the constant term from the original quadratic equation, not the product of the roots after substitution.
CThis is the sum of the x-coordinates x₁ + x₂, not their product.
DThis results from incorrectly applying Vieta's formulas with the wrong sign.
What to do after easy
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