X^2+10x+9=15

Solution for X^2+10x+9=15 equation:

X^2+10X+9=15

We move all terms to the left:

X^2+10X+9-(15)=0

We add all the numbers together, and all the variables

X^2+10X-6=0

a = 1; b = 10; c = -6;
Δ = b2-4ac
Δ = 102-4·1·(-6)
Δ = 124
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:

$\sqrt{\Delta}=\sqrt{124}=\sqrt{4*31}=\sqrt{4}*\sqrt{31}=2\sqrt{31}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-2\sqrt{31}}{2*1}=\frac{-10-2\sqrt{31}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+2\sqrt{31}}{2*1}=\frac{-10+2\sqrt{31}}{2}
$