-4x2+12x+15=-25

Solution for -4x2+12x+15=-25 equation:

-4x^2+12x+15=-25

We move all terms to the left:

-4x^2+12x+15-(-25)=0

We add all the numbers together, and all the variables

-4x^2+12x+40=0

a = -4; b = 12; c = +40;
Δ = b2-4ac
Δ = 122-4·(-4)·40
Δ = 784
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{784}=28$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-28}{2*-4}=\frac{-40}{-8}
=+5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+28}{2*-4}=\frac{16}{-8}
=-2
$