9*x2-7=18

Solution for 9*x2-7=18 equation:

9x^2-7=18

We move all terms to the left:

9x^2-7-(18)=0

We add all the numbers together, and all the variables

9x^2-25=0

a = 9; b = 0; c = -25;
Δ = b2-4ac
Δ = 02-4·9·(-25)
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-30}{2*9}=\frac{-30}{18}
=-1+2/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+30}{2*9}=\frac{30}{18}
=1+2/3
$