The equation is .

Combine like terms using distributive property: .

Apply zero product property: If ab = 0 then a = 0, b = 0.

First .

Second .

Apply addition property of equality: If a = b then a b = b a.

Subtract 4 from each side.

Check:

To check the solution substitute z = 0 in .

The first solution z = 0 is true.

To check the solution substitute in .

The second solution is true.

The values of z = 0, 4.