25x2-30x+9=81

Solution for 25x2-30x+9=81 equation:

25x^2-30x+9=81

We move all terms to the left:

25x^2-30x+9-(81)=0

We add all the numbers together, and all the variables

25x^2-30x-72=0

a = 25; b = -30; c = -72;
Δ = b2-4ac
Δ = -302-4·25·(-72)
Δ = 8100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{8100}=90$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30)-90}{2*25}=\frac{-60}{50}
=-1+1/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+90}{2*25}=\frac{120}{50}
=2+2/5
$