80-x=90-x2

Solution for 80-x=90-x2 equation:

80-x=90-x2

We move all terms to the left:

80-x-(90-x2)=0

We add all the numbers together, and all the variables

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

We add all the numbers together, and all the variables

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

x^2-1x-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}
$