15x^2-21x=18

Solution for 15x^2-21x=18 equation:

15x^2-21x=18

We move all terms to the left:

15x^2-21x-(18)=0

a = 15; b = -21; c = -18;
Δ = b2-4ac
Δ = -212-4·15·(-18)
Δ = 1521
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1521}=39$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-39}{2*15}=\frac{-18}{30}
=-3/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+39}{2*15}=\frac{60}{30}
=2
$