63.75=1.15x^2+7x

Solution for 63.75=1.15x^2+7x equation:

63.75=1.15x^2+7x

We move all terms to the left:

63.75-(1.15x^2+7x)=0

We get rid of parentheses

-1.15x^2-7x+63.75=0

a = -1.15; b = -7; c = +63.75;
Δ = b2-4ac
Δ = -72-4·(-1.15)·63.75
Δ = 342.25
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)-\sqrt{342.25}}{2*-1.15}=\frac{7-\sqrt{342.25}}{-2.3}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+\sqrt{342.25}}{2*-1.15}=\frac{7+\sqrt{342.25}}{-2.3}
$