X^2+15x=-55

Solution for X^2+15x=-55 equation:

X^2+15X=-55

We move all terms to the left:

X^2+15X-(-55)=0

We add all the numbers together, and all the variables

X^2+15X+55=0

a = 1; b = 15; c = +55;
Δ = b2-4ac
Δ = 152-4·1·55
Δ = 5
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{-(15)-\sqrt{5}}{2*1}=\frac{-15-\sqrt{5}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+\sqrt{5}}{2*1}=\frac{-15+\sqrt{5}}{2}
$