diketahui suatu barisan aritmatika dengan U3=7 dan U5 19 tentukan! a.beda barisan b. suku pertama c.suku ke 9

U3 = 7
U5 = 19

B = U5-U3/5-3
B = 19-7/2
B = 12/2
B = 6

A = U3 – 2B
A = 7 – 2(6)
A = 7 – 12
A = -5

U9 = a + (n-1)b
U9 = -5 + (8)6
U9 = -5 + 48
U9 = 43

U3 = a + 2b
7 = a + 2b … (persamaan 1)
U5= a + 4b
19 = a + 4b … (persamaan 2)
a + 2b = 7
a + 4b = 19
—————– –
-2b=-12
b = -12 : -2
b = 6 (beda = 6)
a + 2b = 7
a + 2 x 6 =7
a + 12 = 7
a = 7 – 12
a = -5 (suku pertama)
U9 = a + 8b
= -5 + 8 x 6
= -5 + 48
=43