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C2 Binomial expansions - one urgent question!!

username1479085

hey

could someone explain how to find a term or coefficient in a binomial expansion please?

for example,

1. find the term of x^5 in the expansion of (5-2x)^8

2. find the coefficient of 1/x^3 in the expansion of [2-(3/2x)^7

thanks!

Kevin De Bruyne

Original post by latenightmadness

hey

could someone explain how to find a term or coefficient in a binomial expansion please?

for example,

1. find the term of x^5 in the expansion of (5-2x)^8

2. find the coefficient of 1/x^3 in the expansion of [2-(3/2x)^7

thanks!

If you look in the formula booklet at the expansaion of (a+b)^n, you can define a,b, and n accordingly. For example, in q1, a=5, b = -2x, n = 8. So we are interested in x^5, which translates to finding the term with b^5 in it (and you should be able to work out what it's multiplied by by using the formula).

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