Ad yg tahu no 5 pliss kak bantu

A.
gampang bro..
Un = a.n + b
U(n-1) = a.n-1 + b
jadi :
Un – U(n-1) =
a.n + b – (a.(n-1) + b) =
a.n + b – an + a – b =
a ( terbukti)

b. Un = ab^(n-1)
U(n-1) = ab^(n-1-1) = ab^(n-1).ab^-1
jadi :
Un / U(n-1) =
a.b^n.b^-1 / a.b^n.b^-1.b^-1 =
1 / b^-1 =
1/ (1/b) =
b (terbukti)