Question

13
(i) (7p + 9q) (7p - 9q)​

Answer 1

Answer:

$49 {p}^{2} - 81 {q}^{2}$

Step-by-step explanation:

Use this identity to get the answer

$(x + y)(x - y) = {x}^{2} - {y}^{2}$

Answer 2

(a+b)(a-b) = a²-b²

(7p)²-(9q)²

= 49p²-81q²