9x^2-100=21

Solution for 9x^2-100=21 equation:

9x^2-100=21

We move all terms to the left:

9x^2-100-(21)=0

We add all the numbers together, and all the variables

9x^2-121=0

a = 9; b = 0; c = -121;
Δ = b2-4ac
Δ = 02-4·9·(-121)
Δ = 4356
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4356}=66$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-66}{2*9}=\frac{-66}{18}
=-3+2/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+66}{2*9}=\frac{66}{18}
=3+2/3
$