30=7.5x2

Solution for 30=7.5x2 equation:

30=7.5x^2

We move all terms to the left:

30-(7.5x^2)=0

We get rid of parentheses

-7.5x^2+30=0

a = -7.5; b = 0; c = +30;
Δ = b2-4ac
Δ = 02-4·(-7.5)·30
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*-7.5}=\frac{-30}{-15}
=+2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+30}{2*-7.5}=\frac{30}{-15}
=-2
$