Description
I'm trying to solve x^2+7x+y+8 =0 and -10x^2-59x+y-91=0 my teacher gives us the answer which is (-3,4) but she wants us to set it up as y=? and do it that way
Explanation & Answer
Thank you for the opportunity to help you with your question!
First step: isolate the y in both equations
y(1)=-x^2-7x-8
y(2)=10x^2+59x+91
With y on only one side of the equation, what we're really being asked to do is find the values of x for which y(1) is equal to y(2). And then we solve for what that value is :)
Set them equal:
y(1)=y(2), or
-x^2 -7x -8 = 10x^2 +59x +91
Isolate x on one side:
-7x - 8 = 11x^2 + 59x + 91
-8 = 11x^2 + 66x + 91
11x^2 + 66x + 99 = 0
11(x^2 + 6x + 9) = 0
x^2 + 6x + 9 = 0
(x+3)(x+3)= 0
x = -3
Solve either equation for x = -3:
y(1) = - (-3)^2 - 7(3) - 8 = -12 - 8 = 4 :)
(-3, 4)
Review
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