(7y+9)(y-2)=0

Solution for (7y+9)(y-2)=0 equation:

(7y+9)(y-2)=0

We multiply parentheses ..

(+7y^2-14y+9y-18)=0

We get rid of parentheses

7y^2-14y+9y-18=0

We add all the numbers together, and all the variables

7y^2-5y-18=0

a = 7; b = -5; c = -18;
Δ = b2-4ac
Δ = -52-4·7·(-18)
Δ = 529
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{529}=23$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-23}{2*7}=\frac{-18}{14}
=-1+2/7
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+23}{2*7}=\frac{28}{14}
=2
$