7-5y=4y*(8-6)-64

Solution for 7-5y=4y*(8-6)-64 equation:

7-5y=4y(8-6)-64

We move all terms to the left:

7-5y-(4y(8-6)-64)=0

We add all the numbers together, and all the variables

-5y-(4y2-64)+7=0

We get rid of parentheses

-5y-4y2+64+7=0

We add all the numbers together, and all the variables

-4y^2-5y+71=0

a = -4; b = -5; c = +71;
Δ = b2-4ac
Δ = -52-4·(-4)·71
Δ = 1161
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{1161}=\sqrt{9*129}=\sqrt{9}*\sqrt{129}=3\sqrt{129}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-3\sqrt{129}}{2*-4}=\frac{5-3\sqrt{129}}{-8}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+3\sqrt{129}}{2*-4}=\frac{5+3\sqrt{129}}{-8}
$