(x-2)(-x+9)=0

Solution for (x-2)(-x+9)=0 equation:

(x-2)(-x+9)=0

We add all the numbers together, and all the variables

(x-2)(-1x+9)=0

We multiply parentheses ..

(-1x^2+9x+2x-18)=0

We get rid of parentheses

-1x^2+9x+2x-18=0

We add all the numbers together, and all the variables

-1x^2+11x-18=0

a = -1; b = 11; c = -18;
Δ = b2-4ac
Δ = 112-4·(-1)·(-18)
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(11)-7}{2*-1}=\frac{-18}{-2}
=+9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(11)+7}{2*-1}=\frac{-4}{-2}
=+2
$