-28=7(x-7)x=

Solution for -28=7(x-7)x= equation:

-28=7(x-7)x=

We move all terms to the left:

-28-(7(x-7)x)=0


We calculate terms in parentheses: -(7(x-7)x), so:

7(x-7)x

We multiply parentheses

7x^2-49x

Back to the equation:

-(7x^2-49x)


We get rid of parentheses

-7x^2+49x-28=0

a = -7; b = 49; c = -28;
Δ = b2-4ac
Δ = 492-4·(-7)·(-28)
Δ = 1617
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:

$\sqrt{\Delta}=\sqrt{1617}=\sqrt{49*33}=\sqrt{49}*\sqrt{33}=7\sqrt{33}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(49)-7\sqrt{33}}{2*-7}=\frac{-49-7\sqrt{33}}{-14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(49)+7\sqrt{33}}{2*-7}=\frac{-49+7\sqrt{33}}{-14}
$