Given that the area of a rectangle is (4a & sup2; - 81) CM & sup2; its length is (2a + 9) cm, then what is its width?

Given that the area of a rectangle is (4a & sup2; - 81) CM & sup2; its length is (2a + 9) cm, then what is its width?

Its width
=(4a²-81)/(2a+9)、
=(2a+9)(2a-9)/(2a+9)
=2a-9cm