-42x=3x^2+144

Solution for -42x=3x^2+144 equation:

-42x=3x^2+144

We move all terms to the left:

-42x-(3x^2+144)=0

We get rid of parentheses

-3x^2-42x-144=0

a = -3; b = -42; c = -144;
Δ = b2-4ac
Δ = -422-4·(-3)·(-144)
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-42)-6}{2*-3}=\frac{36}{-6}
=-6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-42)+6}{2*-3}=\frac{48}{-6}
=-8
$