-7x2+21=14

Solution for -7x2+21=14 equation:

-7x^2+21=14

We move all terms to the left:

-7x^2+21-(14)=0

We add all the numbers together, and all the variables

-7x^2+7=0

a = -7; b = 0; c = +7;
Δ = b2-4ac
Δ = 02-4·(-7)·7
Δ = 196
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

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