Question

Help please me with this #3

Answer 1

`a_n = (-1)^(n+1) n^2\\\\a_1 = (-1)^(1+1) \cdot 1^2 = (-1)^2 = 1\\\\a_2= (-1)^(2+1) \cdot 2^2 = (-1)^3 \cdot 4 = -4\\\\a_3 = (-1)^(3+1) \cdot 3^2 = (-1)^4 \cdot 9 = 9\\\\a_4 = (-1)^(4+1) \cdot 4^2 = (-1)^5 \cdot 16 = -16\\\\\text{The first four terms are:}~ 1, -4,~ 9, -16`