25x^2-20x+4=81

Solution for 25x^2-20x+4=81 equation:

25x^2-20x+4=81

We move all terms to the left:

25x^2-20x+4-(81)=0

We add all the numbers together, and all the variables

25x^2-20x-77=0

a = 25; b = -20; c = -77;
Δ = b2-4ac
Δ = -202-4·25·(-77)
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{-(-20)-90}{2*25}=\frac{-70}{50}
=-1+2/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+90}{2*25}=\frac{110}{50}
=2+1/5
$