120=1,5x^2+3x

Solution for 120=1,5x^2+3x equation:

120=1.5x^2+3x

We move all terms to the left:

120-(1.5x^2+3x)=0

We get rid of parentheses

-1.5x^2-3x+120=0

a = -1.5; b = -3; c = +120;
Δ = b2-4ac
Δ = -32-4·(-1.5)·120
Δ = 729
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{729}=27$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-27}{2*-1.5}=\frac{-24}{-3}
=+8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+27}{2*-1.5}=\frac{30}{-3}
=-10
$