When doing questions in binomial to find the greatest term, we first have to take a ratio of T(r+1)/T(r). But my question is that do we have to derive the ratio every time or can we just directly write T(r+1)/T(r)= (n-r+1)/r * b/a?
Last edited by Green Yoda; 22 Aug 2017 at 12:04 PM.
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It's usually 3 marks so derive but check with formula
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Marks are given for the derivation, so it would be best to derive the ratio everytime
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1 out of 3 at best if you use that formula.
The formula only works for simple single expansions. If you were to find the greatest term of something more complicated like (3+x)^{n}+(1+2x)^{n} you can't exactly use the formula. However, the principle of finding the largest value of k such that T(k+1)>T(k), where T(k+1) is general term of the entire expansion, is still valid (it will just look very different to your standard case).
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