Binomial Theorem 1 Question 22

24.

The expression [x+(x31)1/2]5+[x(x31)1/2]5 is a polynomial of degree

(1992, 2M)

(a) 5

(b) 6

(c) 7

(d) 8

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Answer:

Correct Answer: 24. (c)

Solution:

  1. We know that,

(a+b)5+(ab)5=5C0a5+5C1a4b+5C2a3b2+5C3a2b3+5C4ab4+5C5b5+5C0a5C1a4b+5C2a3b25C3a2b3+5C4ab45C5b5=2[a5+10a3b2+5ab4][x+(x31)1/2]5+[x(x31)1/2]5=2[x5+10x3(x31)+5x(x31)2]

Therefore, the given expression is a polynomial of degree 7.



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