3x-9x(2x+10)=100

Solution for 3x-9x(2x+10)=100 equation:

3x-9x(2x+10)=100

We move all terms to the left:

3x-9x(2x+10)-(100)=0

We multiply parentheses

-18x^2+3x-90x-100=0

We add all the numbers together, and all the variables

-18x^2-87x-100=0

a = -18; b = -87; c = -100;
Δ = b2-4ac
Δ = -872-4·(-18)·(-100)
Δ = 369
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{369}=\sqrt{9*41}=\sqrt{9}*\sqrt{41}=3\sqrt{41}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-87)-3\sqrt{41}}{2*-18}=\frac{87-3\sqrt{41}}{-36}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-87)+3\sqrt{41}}{2*-18}=\frac{87+3\sqrt{41}}{-36}
$