(x+3)(x+3)=91

Solution for (x+3)(x+3)=91 equation:

(x+3)(x+3)=91

We move all terms to the left:

(x+3)(x+3)-(91)=0

We multiply parentheses ..

(+x^2+3x+3x+9)-91=0

We get rid of parentheses

x^2+3x+3x+9-91=0

We add all the numbers together, and all the variables

x^2+6x-82=0

a = 1; b = 6; c = -82;
Δ = b2-4ac
Δ = 62-4·1·(-82)
Δ = 364
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:

$\sqrt{\Delta}=\sqrt{364}=\sqrt{4*91}=\sqrt{4}*\sqrt{91}=2\sqrt{91}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-2\sqrt{91}}{2*1}=\frac{-6-2\sqrt{91}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+2\sqrt{91}}{2*1}=\frac{-6+2\sqrt{91}}{2}
$