Question
If (1+ax)n = 1 + 8x + 24 x2 + ......, then the value of a and n is
Answer: Option A
:
A
As given (1+ax)n = 1 + 8x + 24x2 + .........
⇒ 1 + n1ax + n(n−1)1.2a2x2 + ......... = 1 + 8x + 24x2 + ...........
⇒na = 8, n(n−1)1.2a2 = 24⇒ na(n-1)a = 48
⇒8(8 -a) = 48⇒ 8 - a = 6⇒ a = 2⇒ n = 4.
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A
As given (1+ax)n = 1 + 8x + 24x2 + .........
⇒ 1 + n1ax + n(n−1)1.2a2x2 + ......... = 1 + 8x + 24x2 + ...........
⇒na = 8, n(n−1)1.2a2 = 24⇒ na(n-1)a = 48
⇒8(8 -a) = 48⇒ 8 - a = 6⇒ a = 2⇒ n = 4.
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