25x^2+81x=90

Solution for 25x^2+81x=90 equation:

25x^2+81x=90

We move all terms to the left:

25x^2+81x-(90)=0

a = 25; b = 81; c = -90;
Δ = b2-4ac
Δ = 812-4·25·(-90)
Δ = 15561
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:

$\sqrt{\Delta}=\sqrt{15561}=\sqrt{9*1729}=\sqrt{9}*\sqrt{1729}=3\sqrt{1729}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(81)-3\sqrt{1729}}{2*25}=\frac{-81-3\sqrt{1729}}{50}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(81)+3\sqrt{1729}}{2*25}=\frac{-81+3\sqrt{1729}}{50}
$