42x2-15=0

Solution for 42x2-15=0 equation:

42x^2-15=0

a = 42; b = 0; c = -15;
Δ = b2-4ac
Δ = 02-4·42·(-15)
Δ = 2520
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:

$\sqrt{\Delta}=\sqrt{2520}=\sqrt{36*70}=\sqrt{36}*\sqrt{70}=6\sqrt{70}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-6\sqrt{70}}{2*42}=\frac{0-6\sqrt{70}}{84}
=-\frac{6\sqrt{70}}{84}
=-\frac{\sqrt{70}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+6\sqrt{70}}{2*42}=\frac{0+6\sqrt{70}}{84}
=\frac{6\sqrt{70}}{84}
=\frac{\sqrt{70}}{14}
$