X^2+6x+2x+21=180

Solution for X^2+6x+2x+21=180 equation:

X^2+6X+2X+21=180

We move all terms to the left:

X^2+6X+2X+21-(180)=0

We add all the numbers together, and all the variables

X^2+8X-159=0

a = 1; b = 8; c = -159;
Δ = b2-4ac
Δ = 82-4·1·(-159)
Δ = 700
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:

$\sqrt{\Delta}=\sqrt{700}=\sqrt{100*7}=\sqrt{100}*\sqrt{7}=10\sqrt{7}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-10\sqrt{7}}{2*1}=\frac{-8-10\sqrt{7}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+10\sqrt{7}}{2*1}=\frac{-8+10\sqrt{7}}{2}
$