1.

Find the sum to n terms : 1+ 2x + 3x^2 + 4x^3 + … ,xne 1 :

Answer»

`1+nx^n`
`(X(x+1))/(2) + x^n`
`(1-x^n)/((1-x)^2)`
`{(1-x^n)/((1-x)^2) - (nx^n)/((1-x))}`

ANSWER :D


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