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- Dec 8th 2007, 11:42 AMoceanmdBinomial Theorem
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- Dec 8th 2007, 11:54 AMSoroban
Hello, oceanmd!

Your concern is well-founded.

There may be typo in the second problem . . .

It should have looked like this:

. . Problem 2

. . Find the fifth term of $\displaystyle (ab-3)^{10}$

. . Answer: .$\displaystyle {10\choose6}(ab)^6(-3)^4 = 210 * 81(ab)^6 = 17,010(ab)^6$

- Dec 8th 2007, 12:17 PMPlato
- Dec 8th 2007, 12:19 PMangel.white
Yes, I interpreted ab to be two different constants, so $\displaystyle ab^6=a*b^6$ which is wrong.

An easy way to remedy it would just be to place brackets around each ab pair, then you wouldn't have to rewrite it, and it's safer too, because if your instructor is wanting $\displaystyle ab^6$ (this would seem unlikely) then you won't get it wrong if you write $\displaystyle (ab)^6$ but you would get it wrong if you wrote $\displaystyle a^6b^6$. But at the same time, if the instructor is wanting $\displaystyle a^6b^6$ (most likely) you still won't get it wrong if you write $\displaystyle (ab)^6$. So be on the safe side, and just put parenthases around these. And make sure you know how to do it if they replace the variables with actual numbers, ie the 6th term of $\displaystyle (2*3-3)^{10}$