-x^2-7x+7=-2x^2

Solution for -x^2-7x+7=-2x^2 equation:

-x^2-7x+7=-2x^2

We move all terms to the left:

-x^2-7x+7-(-2x^2)=0

We add all the numbers together, and all the variables

-1x^2-(-2x^2)-7x+7=0

We get rid of parentheses

-1x^2+2x^2-7x+7=0

We add all the numbers together, and all the variables

x^2-7x+7=0

a = 1; b = -7; c = +7;
Δ = b2-4ac
Δ = -72-4·1·7
Δ = 21
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-7)-\sqrt{21}}{2*1}=\frac{7-\sqrt{21}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+\sqrt{21}}{2*1}=\frac{7+\sqrt{21}}{2}
$