(3z+2)*(3z-2)=21

Solution for (3z+2)*(3z-2)=21 equation:

Simplifying
(3z + 2)(3z + -2) = 21

Reorder the terms:
(2 + 3z)(3z + -2) = 21

Reorder the terms:
(2 + 3z)(-2 + 3z) = 21

Multiply (2 + 3z) * (-2 + 3z)
(2(-2 + 3z) + 3z * (-2 + 3z)) = 21
((-2 * 2 + 3z * 2) + 3z * (-2 + 3z)) = 21
((-4 + 6z) + 3z * (-2 + 3z)) = 21
(-4 + 6z + (-2 * 3z + 3z * 3z)) = 21
(-4 + 6z + (-6z + 9z2)) = 21

Combine like terms: 6z + -6z = 0
(-4 + 0 + 9z2) = 21
(-4 + 9z2) = 21

Solving
-4 + 9z2 = 21

Solving for variable 'z'.

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

Add '4' to each side of the equation.
-4 + 4 + 9z2 = 21 + 4

Combine like terms: -4 + 4 = 0
0 + 9z2 = 21 + 4
9z2 = 21 + 4

Combine like terms: 21 + 4 = 25
9z2 = 25

Divide each side by '9'.
z2 = 2.777777778

Simplifying
z2 = 2.777777778

Take the square root of each side:
z = {-1.666666667, 1.666666667}