21a^2-7a=0

Solution for 21a^2-7a=0 equation:

Simplifying
21a2 + -7a = 0

Reorder the terms:
-7a + 21a2 = 0

Solving
-7a + 21a2 = 0

Solving for variable 'a'.

Factor out the Greatest Common Factor (GCF), '7a'.
7a(-1 + 3a) = 0

Ignore the factor 7.
Subproblem 1
Set the factor 'a' equal to zero and attempt to solve:

Simplifying
a = 0

Solving
a = 0

Move all terms containing a to the left, all other terms to the right.

Simplifying
a = 0
Subproblem 2
Set the factor '(-1 + 3a)' equal to zero and attempt to solve:

Simplifying
-1 + 3a = 0

Solving
-1 + 3a = 0

Move all terms containing a to the left, all other terms to the right.

Add '1' to each side of the equation.
-1 + 1 + 3a = 0 + 1

Combine like terms: -1 + 1 = 0
0 + 3a = 0 + 1
3a = 0 + 1

Combine like terms: 0 + 1 = 1
3a = 1

Divide each side by '3'.
a = 0.3333333333

Simplifying
a = 0.3333333333
Solution
a = {0, 0.3333333333}