# question about QR in topscore.

Discussion in 'DAT Discussions' started by jjw822, Jun 16, 2008.

1. ### jjw822 7+ Year Member

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I searched past threads and they linked some website which are not existing anymore..lol

anyway,, topscore test 2 QR #20, which is the third term in the expansion of (x+)^5??

how would i do this problem???

I have DAT in this saturday.... i am fricking out...

2. ### lemoncurry tequila mockingbird Administrator Dentist 10+ Year Member

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sounds like a typo to me. what are the answer choices? Seems like they want you to expand a quadratic to the fifth power and give the third term (i.e. to the 3rd power).

however, it seems it is missing a number. For example, it should be (x+1)^5 or something. In which case, you should multiply it out: (x+1)(x+1)(x+1)(x+1)(x+1)

(x+1)^2 = x^2 + 2x +1

times (x+1) = x^3 + 3x^2 + 3x + 1

times (x+1) = x^4 + 4x^3 + 6x^2 + 4x + 1

times (x+1) = x^5 + 5x^4 + 10x^3 + 10x^2 + 5x + 1

third term would be 10x^3, if I understand the question correctly.

If you notice the pattern of the answers, it follows the binomial theorem.

http://en.wikipedia.org/wiki/Binomial_theorem

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3. ### jjw822 7+ Year Member

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oops
it is supposed to be (x+3)^5

a. 10x^3
b. 9x^3
c. 90x^3
d. 90x^4
e. 10x^4

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5. ### DentalDeac 2+ Year Member

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So using the binomial theorum the answer would by 90x^3, C.

6. ### jjw822 7+ Year Member

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what is that??

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