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Question

Question: If (1+ x + 2 x<sup>2</sup>)<sup>20</sup> = a<sub>0</sub> + a<sub>1</sub>x + a<sub>2</sub>x<sup>2</su...

If (1+ x + 2 x2)20 = a0 + a1x + a2x2 + ....... + a40 x40 fud a1 + a3 + a5 + ........ + a37 + a39 =

A

4202\frac{4^{20}}{2}

B

4202202\frac{4^{20}–2^{20}}{2}

C

2202\frac{2^{20}}{2}

D

None of these

Answer

4202202\frac{4^{20}–2^{20}}{2}

Explanation

Solution

Put x = 1, x = – 1 and subtract then

(4)20 – 220

= 2[a1 + a3 + ......+a39]