X2=8-5y

Solution for X2=8-5y equation:

X2=8-5X

We move all terms to the left:

X2-(8-5X)=0

We add all the numbers together, and all the variables

X2-(-5X+8)=0

We add all the numbers together, and all the variables

X^2-(-5X+8)=0

We get rid of parentheses

X^2+5X-8=0

a = 1; b = 5; c = -8;
Δ = b2-4ac
Δ = 52-4·1·(-8)
Δ = 57
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-\sqrt{57}}{2*1}=\frac{-5-\sqrt{57}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+\sqrt{57}}{2*1}=\frac{-5+\sqrt{57}}{2}
$