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0
50
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+259

Compute:  $$\dbinom{15}{2}$$

Mr.Owl  Oct 20, 2017

#2
+259
+2

\begin{align*} \dbinom{15}{2} &= \dfrac{15!}{13!2!} \\ &= \dfrac{15\times 14}{2\times 1} \\ &= 15 \times \dfrac{14}{2} \\ &= 15 \times 7 \\ &= \boxed{105}. \end{align*}

Mr.Owl  Oct 20, 2017
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#1
+1

15nCr2 =105

Guest Oct 20, 2017
#2
+259
+2

\begin{align*} \dbinom{15}{2} &= \dfrac{15!}{13!2!} \\ &= \dfrac{15\times 14}{2\times 1} \\ &= 15 \times \dfrac{14}{2} \\ &= 15 \times 7 \\ &= \boxed{105}. \end{align*}

Mr.Owl  Oct 20, 2017
#3
+78557
+1

Very nice, Mr. O   !!!!!!

CPhill  Oct 20, 2017

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