: Use the equation y = -4x to solve for x.
9
x² + y² = 153
y = −4x
If (x, y) is a solution to the system of equations above, what is the value of x²?
-51
3
9
144
Hints
3 answers
Correct. The second equation gives y in terms of x, so a student can use this to rewrite the first equation in terms of x. Substituting −4x for y in the equation x² + y² = 153 gives x² + (−4x)² = 153. This can be simplified to x² + 16x² = 153, or 17x² = 153. Since the question asks for the value of x², not x, dividing both sides of 17x² = 153 by 17 gives the answer: x² = 153/17 = 9.
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actually, there are two values of x , the question is not done
it asked for x , not x^2
from x^2 = 9
x = ± 3
so (x,y) could be (3, -12) or (-3,12)
it asked for x , not x^2
from x^2 = 9
x = ± 3
so (x,y) could be (3, -12) or (-3,12)