168=42x^2

Solution for 168=42x^2 equation:

168=42x^2

We move all terms to the left:

168-(42x^2)=0

a = -42; b = 0; c = +168;
Δ = b2-4ac
Δ = 02-4·(-42)·168
Δ = 28224
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{28224}=168$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-168}{2*-42}=\frac{-168}{-84}
=+2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+168}{2*-42}=\frac{168}{-84}
=-2
$