128=(x+10)x

Solution for 128=(x+10)x equation:

128=(x+10)x

We move all terms to the left:

128-((x+10)x)=0


We calculate terms in parentheses: -((x+10)x), so:

(x+10)x

We multiply parentheses

x^2+10x

Back to the equation:

-(x^2+10x)


We get rid of parentheses

-x^2-10x+128=0

We add all the numbers together, and all the variables

-1x^2-10x+128=0

a = -1; b = -10; c = +128;
Δ = b2-4ac
Δ = -102-4·(-1)·128
Δ = 612
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:

$\sqrt{\Delta}=\sqrt{612}=\sqrt{36*17}=\sqrt{36}*\sqrt{17}=6\sqrt{17}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-6\sqrt{17}}{2*-1}=\frac{10-6\sqrt{17}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+6\sqrt{17}}{2*-1}=\frac{10+6\sqrt{17}}{-2}
$