Question

oyce is trying to solve the equation y = x2 − 8x + 7 using the quadratic formula. She has made an error in one of the steps below. Find the step where Joyce went wrong.

Answer 1

You didn't attach anything, but this is how you should solve this equation: given an equation $ax^2+bx+c=0$ the solutions are

$x_{1,2} = \dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$

In your case, the values are $a=1,\ b=-8,\ c=7$. If you plug these values inside the solving formula, you have

$x_{1,2} = \dfrac{8\pm\sqrt{64-4\cdot 1\cdot 7}}{2\cdot 1} = \dfrac{8\pm\sqrt{64-28}}{2} = \dfrac{8\pm\sqrt{36}}{2} = \dfrac{8\pm6}{2} = 4\pm3$

So, the two solutions are 1 and 7