-4x2+36x-3.75=0

Solution for -4x2+36x-3.75=0 equation:

-4x^2+36x-3.75=0

a = -4; b = 36; c = -3.75;
Δ = b2-4ac
Δ = 362-4·(-4)·(-3.75)
Δ = 1236
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:

$\sqrt{\Delta}=\sqrt{1236}=\sqrt{4*309}=\sqrt{4}*\sqrt{309}=2\sqrt{309}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(36)-2\sqrt{309}}{2*-4}=\frac{-36-2\sqrt{309}}{-8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(36)+2\sqrt{309}}{2*-4}=\frac{-36+2\sqrt{309}}{-8}
$