Doubt from infinite series

#1

#2

Please tell @Dishi_2020 what we have to solved in this problem??

#3

Find value of y

#4

Are u sure 3x² term is there and is the answer 1/1-x?

#5

Is it 1/(1-x) ?

#6

Answer is 1/1-x

#7

If 3x² term exists then your answer is not correct

#8

Answer is not looking good so i have posted initial steps you can differentiate it and find the result

1 Like
#9

You have made a slight mistake. The Coeff of x^6 will be 4 not 3. I see what you were thinking. But x^6 will also be formed from x, x^2, x^3. You have only considered coeef which formed from multiplication of 2 terms. But multiplication of 3/4/5.. terms may also form the coeff.