21a^2-2a-3=0

Solution for 21a^2-2a-3=0 equation:

Simplifying
21a2 + -2a + -3 = 0

Reorder the terms:
-3 + -2a + 21a2 = 0

Solving
-3 + -2a + 21a2 = 0

Solving for variable 'a'.

Factor a trinomial.
(-1 + -3a)(3 + -7a) = 0

Subproblem 1
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
Subproblem 2
Set the factor '(3 + -7a)' equal to zero and attempt to solve:

Simplifying
3 + -7a = 0

Solving
3 + -7a = 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 + -7a = 0 + -3

Combine like terms: 3 + -3 = 0
0 + -7a = 0 + -3
-7a = 0 + -3

Combine like terms: 0 + -3 = -3
-7a = -3

Divide each side by '-7'.
a = 0.4285714286

Simplifying
a = 0.4285714286
Solution
a = {-0.3333333333, 0.4285714286}