Aritmetika Tentukan nilai a jika diketahui. a.U4=21,b=2 b.U12=25,b=3 c.U8=52,b=8 d.U3=4*1/2,U4=5*1/2

a. 21 = a+(4-1)2
   21 = a + 6 --> a = 15
b.25 = a +(12-1)3
   25 = a+33 --> a  = -8
c. 52 = a + (8-1)8
 b  52 = a + 56 --> a = -4
d. u3 =  4 1/2 ---> a + 2b = 4 1/2
   u4 = 5 1/2 ---> a + 3b = 5 1/2
b = 1
a + 3(1) = 5 1/2
a = 2 1/2

langsung aja yy

A.
U4 = a + 3b
21 = a + 3(2)
a = 21 - 6
a = 15

B.
U12 = a + 11b
25 = a + 11(3)
a = 25 - 33
a = -8

C.
U8 = a + 7b
52 = a + 7(8)
a = 52 - 56
a = -4

D.
maaf gak paham ^_^