x^2+x=9.88

Solution for x^2+x=9.88 equation:

x^2+x=9.88

We move all terms to the left:

x^2+x-(9.88)=0

We add all the numbers together, and all the variables

x^2+x-9.88=0

a = 1; b = 1; c = -9.88;
Δ = b2-4ac
Δ = 12-4·1·(-9.88)
Δ = 40.52
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{40.52}}{2*1}=\frac{-1-\sqrt{40.52}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{40.52}}{2*1}=\frac{-1+\sqrt{40.52}}{2}
$