21d(d)-7d=0

Solution for 21d(d)-7d=0 equation:

Simplifying
21d(d) + -7d = 0

Multiply d * d
21d2 + -7d = 0

Reorder the terms:
-7d + 21d2 = 0

Solving
-7d + 21d2 = 0

Solving for variable 'd'.

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

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

Simplifying
d = 0

Solving
d = 0

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

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

Simplifying
-1 + 3d = 0

Solving
-1 + 3d = 0

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

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

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

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

Divide each side by '3'.
d = 0.3333333333

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