Question 737282
<pre>
The rth term of (A + B)<sup>N</sup> is  {{{(matrix(2,1,N,r-1))A^(r-1)*B^(N-r+1)}}}

For (x + 3y)<sup>5</sup>        

Substitute x for A, 3y for B, 8 for N, and 5 for r

    {{{(matrix(2,1,8,5-1))(x)^(5-1)*(3y)^(8-5+1)}}}

    {{{(matrix(2,1,8,4))x^4*(3y)^4}}}

    {{{(matrix(2,1,8,4))x^4*3^4y^4}}}

    {{{(matrix(2,1,8,4))x^4*81y^4}}}

Now we use  nCr to find {{{(matrix(2,1,8,4))}}} 

Press ON
Press CLEAR
Press 8
Press MATH
Press left arrow once to highlight PRB
Press 3
          Read 8 nCr
Press 4   Read 8 nCr 4
Press ENTER
          Read 70

Substitute 70 for {{{(matrix(2,1,8,4))}}}

    {{{70x^4*81y^4}}} 
  
    {{{5670x^4*y^4}}}

Edwin</pre>