21x^2=56-14x

Solution for 21x^2=56-14x equation:

21x^2=56-14x

We move all terms to the left:

21x^2-(56-14x)=0

We add all the numbers together, and all the variables

21x^2-(-14x+56)=0

We get rid of parentheses

21x^2+14x-56=0

a = 21; b = 14; c = -56;
Δ = b2-4ac
Δ = 142-4·21·(-56)
Δ = 4900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4900}=70$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(14)-70}{2*21}=\frac{-84}{42}
=-2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(14)+70}{2*21}=\frac{56}{42}
=1+1/3
$