Question 1082744

What is the fourth term in the expansion of (x + 4y)^4?
<pre>{{{(x + 4y)^4}}}
To find a SPECIFIC TERM of a binomial expansion, we use the formula: {{{(a + b)^n = "" [n]C[r - 1](a)^(n - (r - 1))(b)^(r - 1)}}}, where: 
                                                                      r = 4
                                                                      n = 4
                                                                      a = x
                                                                      b = 4y
We then get: 4th term of {{{(x + 4y)^4 = "" [4]C[4 - 1](x)^(4 - (4 - 1))(4y)^(4 - 1)}}} ======> {{{""[4]C[3](x)^1(4y)^3}}} ======> {{{highlight_green(matrix(1,3, 4x * 64y^3, "=", 256xy^3))}}}