In this case, we'll have to carry out several steps to find the solution.
Step 01:
Data:
(x - 9) (5x + 9) = 0
Step 02:
zero-product principle:
(x - 9) (5x + 9) = 0
(x - 9) = 0
x - 9 = 0
x = 9
(5x + 9) = 0
5x + 9 = 0
5x = - 9
x = - 9 / 5
The answer is:
x1 = 9
x2 = - 9 / 5