Q.

Let (1+x+x2+x3+x4)n=a0+a1x+a2x2++a4nx4n, then the value of a1+a6+a11+a1+a2+a3+a4+a6+a7+a8+a9+a11 is equal to ______

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answer is 0.25.

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Detailed Solution

Put x=1  we get  5n=a0+a1+a2+a3+a4+a5+..........
Put x=ei4π3put x=ei6π5
After simplification we get 

a0+a5+a10+=a1+a6+a11+=a2+a7+a12+=a3+a8+a13+..= a4+a9+a14+=5n5=5n1

 Required equals to 5n14×5n1=0.25

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Let (1+x+x2+x3+x4)n=a0+a1x+a2x2+…+a4nx4n, then the value of a1+a6+a11+…a1+a2+a3+a4+a6+a7+a8+a9+a11… is equal to ______