21a^2=6a

Solution for 21a^2=6a equation:

21a^2=6a

We move all terms to the left:

21a^2-(6a)=0

a = 21; b = -6; c = 0;
Δ = b2-4ac
Δ = -62-4·21·0
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-6}{2*21}=\frac{0}{42}
=0
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+6}{2*21}=\frac{12}{42}
=2/7
$