(y-1)(y+7)=0

Solution for (y-1)(y+7)=0 equation:

(y-1)(y+7)=0

We multiply parentheses ..

(+y^2+7y-1y-7)=0

We get rid of parentheses

y^2+7y-1y-7=0

We add all the numbers together, and all the variables

y^2+6y-7=0

a = 1; b = 6; c = -7;
Δ = b2-4ac
Δ = 62-4·1·(-7)
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-8}{2*1}=\frac{-14}{2}
=-7
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+8}{2*1}=\frac{2}{2}
=1
$