sebah barisan bilangan U9=58 dan U10=65 tentukan suku pertamanya

U9=a+(9-1)b
U9=a+8b=58

U10=a+(10-1)b
U10=a+9b=65

a+8b=58
a+9b=65
_______ _
-b=-7
b=7

a+8b=58
a+8(7)=58
a+56=58
a=58-56
a=2

Jadi Suku Awalnya = 2

  U9 ⇒ a + 8b = 58
U10 ⇒ a + 9b = 65
           ----------------- -
                 -b   = -7
                  b   = 7

a + 8b = 58
a + 8 (7) = 58
a = 58 - 56
   = 2

Semoga Membantu!!!