EXPONENTIALS 3

If (2^x-9)(7^2y+8) = (2²⁰)(7²⁸) find x+y.

solution

2^x-9 = 2²⁰

x – 9 = 20

x = 20+9

x = 29

…………………………

7^2y+8 = 7²⁸

2y + 8 = 28

2y = 28 - 8

2y = 20

2y = 20           [dividing by 2 both sides]

2      2

y = 10

……………………

x + y = 29 + 10 = 39.

TRY THIS………….

 NECTA 2008 QN. 3a

If (2^x-7)(7^y+8) = (2²⁰)(7²⁸) find (i)x+y.      (ii) y/x