Answer:
a = 2
b = 5
Explanation:
Given :
(ar^b)^4 = 16r^20 ; a and b are positive integers :
Opening the bracket :
a^4r^4b = 16r^20
a^4 = 16 - - - - - (1)
r^4b = r^20 - - - (2)
a^4 = 16
Take the 4th root of both sides :
(a^4)^(1/4) = 16^1/4
a = 2
From (2)
r^4b = r^20
4b = 20
Divide both sides by 4
4b/4 = 20/4
b = 5
Hence ;
a = 2
b = 5