-3(x+7)(x+7)=-13

Solution for -3(x+7)(x+7)=-13 equation:

-3(x+7)(x+7)=-13

We move all terms to the left:

-3(x+7)(x+7)-(-13)=0

We add all the numbers together, and all the variables

-3(x+7)(x+7)+13=0

We multiply parentheses ..

-3(+x^2+7x+7x+49)+13=0

We multiply parentheses

-3x^2-21x-21x-147+13=0

We add all the numbers together, and all the variables

-3x^2-42x-134=0

a = -3; b = -42; c = -134;
Δ = b2-4ac
Δ = -422-4·(-3)·(-134)
Δ = 156
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:

$\sqrt{\Delta}=\sqrt{156}=\sqrt{4*39}=\sqrt{4}*\sqrt{39}=2\sqrt{39}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-42)-2\sqrt{39}}{2*-3}=\frac{42-2\sqrt{39}}{-6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-42)+2\sqrt{39}}{2*-3}=\frac{42+2\sqrt{39}}{-6}
$