Q.

The number of integral terms in the expansion of (512+718)1016 is          [2025]

1 129  
2 127  
3 130  
4 128  

Ans.

(4)

Tr+1=Cr 101651016r27r/8, represents the (r+1)th term of (51/2+71/8)1016.

As Tr+1 represent an integral term when r is a multiple of 8

i.e., r = 0, 8, 16, 24, ....., 1016

Now, 1016 = 0 + (n – 1)8          [As this form an A.P.]

 n1=127  n=128

So, 128 terms are integral terms.