7a^2+21a=0

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

Simplifying
7a2 + 21a = 0

Reorder the terms:
21a + 7a2 = 0

Solving
21a + 7a2 = 0

Solving for variable 'a'.

Factor out the Greatest Common Factor (GCF), '7a'.
7a(3 + a) = 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 '(3 + a)' equal to zero and attempt to solve:

Simplifying
3 + a = 0

Solving
3 + a = 0

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

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

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

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

Simplifying
a = -3
Solution
a = {0, -3}