2.5x^2-15=0

Solution for 2.5x^2-15=0 equation:

2.5x^2-15=0

a = 2.5; b = 0; c = -15;
Δ = b2-4ac
Δ = 02-4·2.5·(-15)
Δ = 150
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:

$\sqrt{\Delta}=\sqrt{150}=\sqrt{25*6}=\sqrt{25}*\sqrt{6}=5\sqrt{6}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-5\sqrt{6}}{2*2.5}=\frac{0-5\sqrt{6}}{5}
=-\frac{5\sqrt{6}}{5}
=-\sqrt{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+5\sqrt{6}}{2*2.5}=\frac{0+5\sqrt{6}}{5}
=\frac{5\sqrt{6}}{5}
=\sqrt{6}
$