MCQ
If (1 + ax)n = 1 + 8x + 24x2 + .... then a × n is:
- A8
- B12
- C16
- D24
Solution:
(1 + ax)n = 1 + 8x + 24x2 + ..........
⇒ nC0 + nC1(ax) + nC2.(ax)2 + ...... = 1 + 8x + 24ax2 ..........
⇒ 1 + (na)x + nC2.(ax)2 + ...... = 1 + 8x + 24ax2 ..........
Comparing coefficient of x in R.H.S to that in L.H.S.Thus n × a = 8
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