u40= 7 + (40-1) x -2 = -71
thanks ya!
Un = a+(n-1)b
U40= 7+(40-1)-2
= 7+(39x(-2))
=7-78
= -71
U40 ?
7,5,3,1
a = 7
b = U2 - U1
b = 5-7 = -2

U40 = a + 39b
U40 = 7 + 39(-2)
U40 = 7 - 78
U40 = - 71

Jawabanmu

2014-02-24T20:50:45+07:00