(x+12)*(x+3)=45

Solution for (x+12)*(x+3)=45 equation:

(x+12)(x+3)=45

We move all terms to the left:

(x+12)(x+3)-(45)=0

We multiply parentheses ..

(+x^2+3x+12x+36)-45=0

We get rid of parentheses

x^2+3x+12x+36-45=0

We add all the numbers together, and all the variables

x^2+15x-9=0

a = 1; b = 15; c = -9;
Δ = b2-4ac
Δ = 152-4·1·(-9)
Δ = 261
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:

$\sqrt{\Delta}=\sqrt{261}=\sqrt{9*29}=\sqrt{9}*\sqrt{29}=3\sqrt{29}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-3\sqrt{29}}{2*1}=\frac{-15-3\sqrt{29}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+3\sqrt{29}}{2*1}=\frac{-15+3\sqrt{29}}{2}
$