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# Deducing Coefficients?? watch

1. Two questions, that I can't seem to work out.
1. Deduce the coefficient of x2 in the expansion of (3-x)(2+0.5x)8

and

2. Find the term independent of x in the expansion of (x- 2/x2)6

2. (Original post by Affection)
Two questions, that I can't seem to work out.
1. Deduce the coefficient of x2 in the expansion of (3-x)(2+0.5x)8

and

2. Find the term independent of x in the expansion of (x- 2/x2)6

They both follow the same principle - if anything, the second one is easier than the first.

For Q1 you want to work out how you are going to get a term involving x^2 in the final expansion. You have a 3 in the first bracket which mutlplies everything from the second bracket, so you will need the term in x^2 from that second bracket. Then you have a -x in the 1st bracket multiplying everything from the 2nd bracket, so you will need to use the term in x from that second bracket.

Now just combine the 2 parts you have found.

For Q2 use the binomial theorem to write down the general term from the expansion and work out a condition which produces the constant term i.e. power of x = 0.

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Updated: January 22, 2015
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