Question

Evaluate : (5+f)(5-f)​

Answer 1

Evaluate : (5+f)(5-f)

This is in the form of (a+b)(a-b) where a = 5 and b = f.

We know that (a+b)(a-b) = a²-b²

Therefore,

(5+f)(5-f) = 5² - f²

=> (5+f)(5-f) = 25 - f²