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B
a0+a2+a4+......+a2n=14(9n+1+2a2n)
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C
a0+a2+a4+......+a2n=14(9n−1−2a2n)
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D
a0+a2+a4+......+a2n=14(9n+1−2a2n)
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Solution
The correct option is Aa0+a2+a4+......+a2n=14(9n+1+2a2n) (1+x+x2)2n=a0+a1(x)+a2x2+...a4nx4n For x=1, we get 9n=a0+a1+a2+...a4n ... (i) For x=−1 we get 1=a0−a1+a2−...a4n ... (ii) Adding, (i) and (ii), we get 9n+1=2[a0+a2+a4+...a4n]
⇒9n+12=a0+a2+a4+...a4n And ar=a4n−r Now the middle term will be a2n Hence 12[9n+1]=2[a0+a2+...a2n−1]+a2n