25x^2-9=40

Solution for 25x^2-9=40 equation:

25x^2-9=40

We move all terms to the left:

25x^2-9-(40)=0

We add all the numbers together, and all the variables

25x^2-49=0

a = 25; b = 0; c = -49;
Δ = b2-4ac
Δ = 02-4·25·(-49)
Δ = 4900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4900}=70$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-70}{2*25}=\frac{-70}{50}
=-1+2/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+70}{2*25}=\frac{70}{50}
=1+2/5
$