X2+x-3.15=0

Solution for X2+x-3.15=0 equation:

X2+X-3.15=0

We add all the numbers together, and all the variables

X^2+X-3.15=0

a = 1; b = 1; c = -3.15;
Δ = b2-4ac
Δ = 12-4·1·(-3.15)
Δ = 13.6
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{-(1)-\sqrt{13.6}}{2*1}=\frac{-1-\sqrt{13.6}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{13.6}}{2*1}=\frac{-1+\sqrt{13.6}}{2}
$