Resposta :
a) P.A. (4, 4+(1.3), 4+(2.3), 4+(3.3), 4+(4.3) )
PA (4,7,10,13,16)
B) a1=20 r=-4
P.A. (20, 20+(1.-4), 20+(2.-4), 20+(3.-4), 20+(4.-4) )
P.A.(20,16,12,8,4)
PA (4,7,10,13,16)
B) a1=20 r=-4
P.A. (20, 20+(1.-4), 20+(2.-4), 20+(3.-4), 20+(4.-4) )
P.A.(20,16,12,8,4)