(17-x)(9-x)=0

Solution for (17-x)(9-x)=0 equation:

(17-x)(9-x)=0

We add all the numbers together, and all the variables

(-1x+17)(-1x+9)=0

We multiply parentheses ..

(+x^2-9x-17x+153)=0

We get rid of parentheses

x^2-9x-17x+153=0

We add all the numbers together, and all the variables

x^2-26x+153=0

a = 1; b = -26; c = +153;
Δ = b2-4ac
Δ = -262-4·1·153
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-26)-8}{2*1}=\frac{18}{2}
=9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-26)+8}{2*1}=\frac{34}{2}
=17
$