Rule Sequences

Question

Find rule of sequence for -2,6,-12,20,-30

Plz help me.thx

Answer 1

a₁ = -2 = (-1)(2)(1)

 

a₂ = 6 = (-1)²(3)(2)

 

a₃ = -12 = (1)³(4)(3), etd

 

a_n  = (-1)ⁿ(n+1)(n)

 

a_n = (-1)ⁿ(n²+n)