Solveeit Logo

Question

Question: Number of rational terms in the expansion (7<sup>1/3</sup> + 11<sup>1/9</sup>) <sup>6561</sup>...

Number of rational terms in the expansion (71/3 + 111/9) 6561

A

729

B

730

C

731

D

None of these

Answer

730

Explanation

Solution

Tr+1 = 6561Cr (71/3)6561 – r (111/9)r

= 6561Cr 72187. 7–r/3. 11r/9

0 £ r £ 6561

For rational terms r is multiple of 9 0, 9, 81, 27,……6561

Tn = 6561 = a +(n – 1) d = 0 + (n – 1) 9

n = 1 + 65619\frac{6561}{9} = 1 + 729 = 730.