(-28)-7x=-x(7x+7)

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

(-28)-7x=-x(7x+7)

We move all terms to the left:

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

We add all the numbers together, and all the variables

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


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

-x(7x+7)

We multiply parentheses

-7x^2-7x

Back to the equation:

-(-7x^2-7x)


We get rid of parentheses

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

We add all the numbers together, and all the variables

7x^2-28=0

a = 7; b = 0; c = -28;
Δ = b2-4ac
Δ = 02-4·7·(-28)
Δ = 784
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{784}=28$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-28}{2*7}=\frac{-28}{14}
=-2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+28}{2*7}=\frac{28}{14}
=2
$