-10y2-12,5y-2,5=0

Solution for -10y2-12,5y-2,5=0 equation:

-10y^2-12.5y-2.5=0

a = -10; b = -12.5; c = -2.5;
Δ = b2-4ac
Δ = -12.52-4·(-10)·(-2.5)
Δ = 56.25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12.5)-\sqrt{56.25}}{2*-10}=\frac{12.5-\sqrt{56.25}}{-20}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12.5)+\sqrt{56.25}}{2*-10}=\frac{12.5+\sqrt{56.25}}{-20}
$