Question

an=(-1)n.(2n-4) para n=1

Answer 1

a(1) = (-1)(1).2(1)-4
a = -1.(-2)
POrtanto
a = 2

Answer 2

an=(-1)n.(2n-4) para n=1

an=(-1)1.(2*1-4) 
an= (-1 )* (2-4)
an= (-1)*(-2)
an= 2