progressions solve

1. Sum of the series : 1 + 3x + 5x² + 7x³ + .........

2. Sum the series : 1.2.3 + 2.3.4 + 3.4.5. + ......... + to n terms.

3. Sum the series : 1²+ (1² + 2²) + (1²+ 2² + 3²) + ........ to n terms.

5 Answers

1) denote the sum as S

(S) - (S)x = ?

2) t_r = r(r+1)(r+2) u can use formula for summation of r³ , r², and r

alt)the tricky way is writing r(r+1)(r+2) = [(r-1)r(r+1) - r(r+1)(r+2)]/-3

now put r = 1,2,3,... and see what happens when we add them.

plz solve q2

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