25=16a^2

Solution for 25=16a^2 equation:

25=16a^2

We move all terms to the left:

25-(16a^2)=0

a = -16; b = 0; c = +25;
Δ = b2-4ac
Δ = 02-4·(-16)·25
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-40}{2*-16}=\frac{-40}{-32}
=1+1/4
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+40}{2*-16}=\frac{40}{-32}
=-1+1/4
$