28=x(2x-10)

Solution for 28=x(2x-10) equation:

28=x(2x-10)

We move all terms to the left:

28-(x(2x-10))=0


We calculate terms in parentheses: -(x(2x-10)), so:

x(2x-10)

We multiply parentheses

2x^2-10x

Back to the equation:

-(2x^2-10x)


We get rid of parentheses

-2x^2+10x+28=0

a = -2; b = 10; c = +28;
Δ = b2-4ac
Δ = 102-4·(-2)·28
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-18}{2*-2}=\frac{-28}{-4}
=+7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+18}{2*-2}=\frac{8}{-4}
=-2
$