3x(5x-42)=180

Solution for 3x(5x-42)=180 equation:

3x(5x-42)=180

We move all terms to the left:

3x(5x-42)-(180)=0

We multiply parentheses

15x^2-126x-180=0

a = 15; b = -126; c = -180;
Δ = b2-4ac
Δ = -1262-4·15·(-180)
Δ = 26676
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:

$\sqrt{\Delta}=\sqrt{26676}=\sqrt{36*741}=\sqrt{36}*\sqrt{741}=6\sqrt{741}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-126)-6\sqrt{741}}{2*15}=\frac{126-6\sqrt{741}}{30}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-126)+6\sqrt{741}}{2*15}=\frac{126+6\sqrt{741}}{30}
$