Find the value of : log5 625

Let log5 625 = x. ∴ 5x = 625 ⇒ 5x = 54 ⇒ x = 4 Hence, log5 625 = 4.

If a = -1 and b = 2, find :
(i) $a^b + b^a$
(ii) $a^b - b^a$
(iii) $a^b \times b^a$
(iv) $a^b \div b^a$