7x^2+28=100

Solution for 7x^2+28=100 equation:

7x^2+28=100

We move all terms to the left:

7x^2+28-(100)=0

We add all the numbers together, and all the variables

7x^2-72=0

a = 7; b = 0; c = -72;
Δ = b2-4ac
Δ = 02-4·7·(-72)
Δ = 2016
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:

$\sqrt{\Delta}=\sqrt{2016}=\sqrt{144*14}=\sqrt{144}*\sqrt{14}=12\sqrt{14}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-12\sqrt{14}}{2*7}=\frac{0-12\sqrt{14}}{14}
=-\frac{12\sqrt{14}}{14}
=-\frac{6\sqrt{14}}{7}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+12\sqrt{14}}{2*7}=\frac{0+12\sqrt{14}}{14}
=\frac{12\sqrt{14}}{14}
=\frac{6\sqrt{14}}{7}
$