(y+1)(y+6)=9

Solution for (y+1)(y+6)=9 equation:

(y+1)(y+6)=9

We move all terms to the left:

(y+1)(y+6)-(9)=0

We multiply parentheses ..

(+y^2+6y+y+6)-9=0

We get rid of parentheses

y^2+6y+y+6-9=0

We add all the numbers together, and all the variables

y^2+7y-3=0

a = 1; b = 7; c = -3;
Δ = b2-4ac
Δ = 72-4·1·(-3)
Δ = 61
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-\sqrt{61}}{2*1}=\frac{-7-\sqrt{61}}{2}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+\sqrt{61}}{2*1}=\frac{-7+\sqrt{61}}{2}
$