Select a suitable identity and find the following products
(7d – 9e) (7d – 9e)

Question

Select a suitable identity and find the following products(7d – 9e) (7d – 9e)

Philoid · Accepted Answer

Given: (7d – 9e) (7d – 9e),it is a product of 2 binomial expressions which have the same terms 7d – 9e and 7d – 9e.

Now when we compare these expressions with the identities, we

find it in the form of (a-b)²,where a = 7d and b = 9e,

The identity (a-b)² = a²-2ab + b²,

Hence, (7d – 9e) (7d – 9e) = (7d-9e)² = (7d)²-2(7d)(9e) + (9e)² = 49d²-126de + 81e²