maths question

Arrange 3729, 9239, 2739 and 7293 in ascending order


3^729


9^239 = (3^2)^239 = 3^478

27^39 = (3^3)^39 = 3^117

729^3 = (3^6)^3 = 3^18

729^3 < 27^39 < 9^239 < 3^729
1)9*3^n - 3^n


= 9 * 3^n - 1 * 3^n ,take the common factor 3^n :


= (9 - 1) (3^n)


2)


[5^(n+3) - 5^(n+1)] / (3 * 5^n)


= [(5^n) * 5^3 - (5^n) * 5] / (3 * 5^n)


= (5^n) * (5^3 - 5) / (3 * 5^n)


= (5^3 - 5) / 3


= (125 - 5) / 3


= 40