Find the sum of the series 1.2 + 2.3x + 3.4x^2 + .....
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3
the answer is 4.5x^4
it is correct
it is correct
Answered by
5
Answer:
Step-by-step explanation:
1rst order differences; 4,6,8,10,....
2nd order differences;2,2,2,2,....
Scale of the series=(1-x)^(n+1). (Where n is the second order difference hence n=2)
(1-x)^3=1-x^3-3x+3x^2
S=2+6x+12x^2+20x^3+30x^4+....
-3xS=-6x-18x^2-36x^3-60x^4-....
3x^2S=6x^2+18x^3+36x^4+....
-x^3S=-2x^3-6x^4-....
S-3xS+3x^2S-x^3S=2. (Taking S common)
S=2/(1-x)^3 (Answer)
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