8a^2-42a=

Solution for 8a^2-42a= equation:

Simplifying
8a2 + -42a = 0

Reorder the terms:
-42a + 8a2 = 0

Solving
-42a + 8a2 = 0

Solving for variable 'a'.

Factor out the Greatest Common Factor (GCF), '2a'.
2a(-21 + 4a) = 0

Ignore the factor 2.
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 '(-21 + 4a)' equal to zero and attempt to solve:

Simplifying
-21 + 4a = 0

Solving
-21 + 4a = 0

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

Add '21' to each side of the equation.
-21 + 21 + 4a = 0 + 21

Combine like terms: -21 + 21 = 0
0 + 4a = 0 + 21
4a = 0 + 21

Combine like terms: 0 + 21 = 21
4a = 21

Divide each side by '4'.
a = 5.25

Simplifying
a = 5.25
Solution
a = {0, 5.25}