90-x2=80-x

Solution for 90-x2=80-x equation:

90-x2=80-x

We move all terms to the left:

90-x2-(80-x)=0

We add all the numbers together, and all the variables

-x2-(-1x+80)+90=0

We add all the numbers together, and all the variables

-1x^2-(-1x+80)+90=0

We get rid of parentheses

-1x^2+1x-80+90=0

We add all the numbers together, and all the variables

-1x^2+x+10=0

a = -1; b = 1; c = +10;
Δ = b2-4ac
Δ = 12-4·(-1)·10
Δ = 41
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{-(1)-\sqrt{41}}{2*-1}=\frac{-1-\sqrt{41}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{41}}{2*-1}=\frac{-1+\sqrt{41}}{-2}
$