veekayy Posted April 14, 2009 Report Share Posted April 14, 2009 Could anyone help me solve: What is the co-efficient of: x^3 in the expansion of (x+1)^5(2x+1)^4 using the binomial theorem. Thanks!! Reply Link to post Share on other sites More sharing options...
Panserborne Posted April 14, 2009 Report Share Posted April 14, 2009 I guess you'd need to consider each expansion separately at first, then combine them later to find the r term needed. But are you sure this is even in the syllabus? I'm looking at mine now, and it says "The binomial theorem: expansion of (a+b)^n.....Simple applications only" I've only ever seen problems dealing with one expansion, not two. I could be wrong, best ask your math teacher. Reply Link to post Share on other sites More sharing options...
moneyfaery Posted April 14, 2009 Report Share Posted April 14, 2009 You can find the coefficient of x[sup]3[/sup] by finding the coefficients of x[sup]0[/sup]*x[sup]3[/sup], x*x[sup]2[/sup], x[sup]2[/sup]*x, and x[sup]3[/sup]*x[sup]0[/sup] individually using the Binomial Theorem, of course, then adding everything up. Panserborne, I've seen such questions before but in my hw, haha. Reply Link to post Share on other sites More sharing options...
master135 Posted April 15, 2009 Report Share Posted April 15, 2009 A similar Q was on may 08 paper 2 for math hl (tz1) Reply Link to post Share on other sites More sharing options...
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