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# Plz help

Plz help me in finding 1•2+2•4+3•8+…n•2^n •=multiplication...:-)

Note by Prakher Gaushal
2 years, 7 months ago

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Sorry ,but I didn't have the patience to write it down in $$|LaTeX$$ but couldn't let your doubt unattended , sohere's my solution .

P.S. If you find any mistakes, just tell me . I wrote the solution in a hurry !!! · 2 years, 7 months ago

Thanks · 1 year, 11 months ago

It think I told the same anyway nice to see your handwriting . Is this your backside of your project file? · 2 years, 7 months ago

@U Z Yeah, correctly guessed :) · 2 years, 7 months ago

Great.

Let me echo my comment in this note

$$\sum_{r=1}^{n} rx^r = \frac{x+(nx-n-1)x^{n+1}}{(x-1)^2}$$) is a useful formula to be aware of, to sum scenarios like this.

Staff · 2 years, 7 months ago

slide the series , and multiply it by 2 then take the difference , a g.p will be formed.next is easy · 2 years, 7 months ago

What is the sum for $$n = 1, 2, 3, 4, 5$$? Staff · 2 years, 7 months ago

Can't get what u want to say..... · 2 years, 7 months ago