25n^2-50n+21=0

Solution for 25n^2-50n+21=0 equation:

25n^2-50n+21=0

a = 25; b = -50; c = +21;
Δ = b2-4ac
Δ = -502-4·25·21
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-50)-20}{2*25}=\frac{30}{50}
=3/5
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-50)+20}{2*25}=\frac{70}{50}
=1+2/5
$