X=16x^2-81

Solution for X=16x^2-81 equation:

X=16X^2-81

We move all terms to the left:

X-(16X^2-81)=0

We get rid of parentheses

-16X^2+X+81=0

a = -16; b = 1; c = +81;
Δ = b2-4ac
Δ = 12-4·(-16)·81
Δ = 5185
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-\sqrt{5185}}{2*-16}=\frac{-1-\sqrt{5185}}{-32}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{5185}}{2*-16}=\frac{-1+\sqrt{5185}}{-32}
$