7y^2-18=15y

Solution for 7y^2-18=15y equation:

7y^2-18=15y

We move all terms to the left:

7y^2-18-(15y)=0

a = 7; b = -15; c = -18;
Δ = b2-4ac
Δ = -152-4·7·(-18)
Δ = 729
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{729}=27$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-27}{2*7}=\frac{-12}{14}
=-6/7
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+27}{2*7}=\frac{42}{14}
=3
$