135=2x(25-x)

Solution for 135=2x(25-x) equation:

135=2x(25-x)

We move all terms to the left:

135-(2x(25-x))=0

We add all the numbers together, and all the variables

-(2x(-1x+25))+135=0


We calculate terms in parentheses: -(2x(-1x+25)), so:

2x(-1x+25)

We multiply parentheses

-2x^2+50x

Back to the equation:

-(-2x^2+50x)


We get rid of parentheses

2x^2-50x+135=0

a = 2; b = -50; c = +135;
Δ = b2-4ac
Δ = -502-4·2·135
Δ = 1420
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:

$\sqrt{\Delta}=\sqrt{1420}=\sqrt{4*355}=\sqrt{4}*\sqrt{355}=2\sqrt{355}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-50)-2\sqrt{355}}{2*2}=\frac{50-2\sqrt{355}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-50)+2\sqrt{355}}{2*2}=\frac{50+2\sqrt{355}}{4}
$