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# Hardest Question On my Grade 10 Math test

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Find the sum of this:

Sn = 1/1x2  +  1/2x3  +  1/3x4  +  1/nx(n+1)

I appreciate all help!

I am in a 2de class and no one of 60 students solved it.

Thanks!

Mar 1, 2019

#1
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When you say something like "2x3", what do you mean by that? are you multiplying 2x by 3? Because that might make it a little easier. or are you using the x as a multiplication sign? If I was right the first time, then I got this answer: Sn = 3n2 + 4x + nx. This is a quadratic formula, but it's hard to factor because of the two variables, and I think the quadratic formula would make it harder. But if you want to try it, then I got  -sqrt{4-3n} if you go the negative route, but positive turns out to be -sqrt{4-3n}/3. I haven't done this sorta stuff in a while, but I'm pretty sure this is right. I can't find any way to determine any variables.

Hope this helps!

Mar 1, 2019
#2
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ITHINK it means (but I am not sure)     1/ (2x^3)

ElectricPavlov  Mar 1, 2019
#3
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Oh well, then that makes it a lot harder. So far I have (3x2 +1.5x + 1)/3x4 + 1/n2 + nx = Sn. I don't know what to do after this point. You could multiply out so it's just one fraction, but I feel like that would just leave you with a really messy equation with tons of exponents.

LagTho  Mar 1, 2019
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it is 1 / 1 times 2 +  1 / 2times 3 etc....

Drazil  Mar 1, 2019