16x^2-81=6

Solution for 16x^2-81=6 equation:

16x^2-81=6

We move all terms to the left:

16x^2-81-(6)=0

We add all the numbers together, and all the variables

16x^2-87=0

a = 16; b = 0; c = -87;
Δ = b2-4ac
Δ = 02-4·16·(-87)
Δ = 5568
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:

$\sqrt{\Delta}=\sqrt{5568}=\sqrt{64*87}=\sqrt{64}*\sqrt{87}=8\sqrt{87}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-8\sqrt{87}}{2*16}=\frac{0-8\sqrt{87}}{32}
=-\frac{8\sqrt{87}}{32}
=-\frac{\sqrt{87}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+8\sqrt{87}}{2*16}=\frac{0+8\sqrt{87}}{32}
=\frac{8\sqrt{87}}{32}
=\frac{\sqrt{87}}{4}
$