7m2-8=398

Solution for 7m2-8=398 equation:

7m^2-8=398

We move all terms to the left:

7m^2-8-(398)=0

We add all the numbers together, and all the variables

7m^2-406=0

a = 7; b = 0; c = -406;
Δ = b2-4ac
Δ = 02-4·7·(-406)
Δ = 11368
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{11368}=\sqrt{196*58}=\sqrt{196}*\sqrt{58}=14\sqrt{58}$
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-14\sqrt{58}}{2*7}=\frac{0-14\sqrt{58}}{14}
=-\frac{14\sqrt{58}}{14}
=-\sqrt{58}
$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+14\sqrt{58}}{2*7}=\frac{0+14\sqrt{58}}{14}
=\frac{14\sqrt{58}}{14}
=\sqrt{58}
$