-10c^2-15c+25=0

Solution for -10c^2-15c+25=0 equation:

-10c^2-15c+25=0

a = -10; b = -15; c = +25;
Δ = b2-4ac
Δ = -152-4·(-10)·25
Δ = 1225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1225}=35$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-35}{2*-10}=\frac{-20}{-20}
=1
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+35}{2*-10}=\frac{50}{-20}
=-2+1/2
$