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# Help me with these Arithmetic sequence/ Geometric sequence/ Simple Interest questions please

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Mar 13, 2021

#1
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A.) Geometric, sum of all terms is gotta be either -infinite, or all of that added up, I don't have the patience to work that out.

B.) No.

C.) 1+2+4+8+16+32+64+128+256=511, so n=9

D.) So uhh, I'm confused, but I think I get it. It's 4550, because 650+600+550+450...+150+100+50+0=4550

Someone smarter than me can do B.) because I'm lazy.

Yay!

Mar 13, 2021
#2
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hey thanks, Varxaax.. i appreciate your time mate

Guest Mar 13, 2021
#3
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textot is going to run over my math with a dump truck, so beware

Varxaax  Mar 13, 2021
#4
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hahah its okay mate..i hope his answer will make sense

Guest Mar 13, 2021
#5
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A) geometric sequence, and the sum is just $$-\frac{512+256+128+\dots+2+1}{512} = \boxed{-\frac{1023}{512}}$$.

(notice that 1023 is one smaller than 1024, which is 2^10)

B) Idk if my solution is even close to optimal, but here it is:

Let the common difference be x. Then,

$$(35-6x)+(35-5x)+(35-4x)+(35-3x)+(35-2x)+(35-x)+(35)+(35+x)=220\\ 8(35) - 20x=220\\ -20x=-60\\ \boxed{x=3}$$

The common difference is therefore equal to 3

The first term is just $$35-6(3)=\boxed{17}$$

varvaax lmao I'm not that good :)

Mar 13, 2021
edited by textot  Mar 13, 2021
edited by textot  Mar 13, 2021
#6
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so the common difference is 3 right ?

Guest Mar 13, 2021