40=25x^2

Solution for 40=25x^2 equation:

40=25x^2

We move all terms to the left:

40-(25x^2)=0

a = -25; b = 0; c = +40;
Δ = b2-4ac
Δ = 02-4·(-25)·40
Δ = 4000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{4000}=\sqrt{400*10}=\sqrt{400}*\sqrt{10}=20\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-20\sqrt{10}}{2*-25}=\frac{0-20\sqrt{10}}{-50}
=-\frac{20\sqrt{10}}{-50}
=-\frac{2\sqrt{10}}{-5}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+20\sqrt{10}}{2*-25}=\frac{0+20\sqrt{10}}{-50}
=\frac{20\sqrt{10}}{-50}
=\frac{2\sqrt{10}}{-5}
$