25x2+40x-9=0

Solution for 25x2+40x-9=0 equation:

25x^2+40x-9=0

a = 25; b = 40; c = -9;
Δ = b2-4ac
Δ = 402-4·25·(-9)
Δ = 2500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2500}=50$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-50}{2*25}=\frac{-90}{50}
=-1+4/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+50}{2*25}=\frac{10}{50}
=1/5
$