(7x)^2=784

Solution for (7x)^2=784 equation:

(7x)^2=784

We move all terms to the left:

(7x)^2-(784)=0

a = 7; b = 0; c = -784;
Δ = b2-4ac
Δ = 02-4·7·(-784)
Δ = 21952
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:

$\sqrt{\Delta}=\sqrt{21952}=\sqrt{3136*7}=\sqrt{3136}*\sqrt{7}=56\sqrt{7}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-56\sqrt{7}}{2*7}=\frac{0-56\sqrt{7}}{14}
=-\frac{56\sqrt{7}}{14}
=-4\sqrt{7}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+56\sqrt{7}}{2*7}=\frac{0+56\sqrt{7}}{14}
=\frac{56\sqrt{7}}{14}
=4\sqrt{7}
$