7x^2-18=0

Solution for 7x^2-18=0 equation:

7x^2-18=0

a = 7; b = 0; c = -18;
Δ = b2-4ac
Δ = 02-4·7·(-18)
Δ = 504
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:

$\sqrt{\Delta}=\sqrt{504}=\sqrt{36*14}=\sqrt{36}*\sqrt{14}=6\sqrt{14}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-6\sqrt{14}}{2*7}=\frac{0-6\sqrt{14}}{14}
=-\frac{6\sqrt{14}}{14}
=-\frac{3\sqrt{14}}{7}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+6\sqrt{14}}{2*7}=\frac{0+6\sqrt{14}}{14}
=\frac{6\sqrt{14}}{14}
=\frac{3\sqrt{14}}{7}
$