31=0.359x^2-7.61x+70.7

Solution for 31=0.359x^2-7.61x+70.7 equation:

31=0.359x^2-7.61x+70.7

We move all terms to the left:

31-(0.359x^2-7.61x+70.7)=0

We get rid of parentheses

-0.359x^2+7.61x-70.7+31=0

We add all the numbers together, and all the variables

-0.359x^2+7.61x-39.7=0

a = -0.359; b = 7.61; c = -39.7;
Δ = b2-4ac
Δ = 7.612-4·(-0.359)·(-39.7)
Δ = 0.9029
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{-(7.61)-\sqrt{0.9029}}{2*-0.359}=\frac{-7.61-\sqrt{0.9029}}{-0.718}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7.61)+\sqrt{0.9029}}{2*-0.359}=\frac{-7.61+\sqrt{0.9029}}{-0.718}
$