u5=23 u7=33 dit u= 20 kalau yg jawab mudah2 dia masuk surga mendapat pahala yg banyak

Bab :Barisan dan Deret
Kelas : VIII ( K13 )

U5 = U1 + 4b = 23
U7 = U1 + 6b = 33
••••••••••••••••••••••••
=======> -2b = -10
=======> b = 5

U5 = U1 + 4b
23 = U1 + 4(5)
U1 = 23 - 20
U1 = 3

U20 = U1 + 19b
U20 = 3 + 19(5)
U20 = 3 + 95
U20 = 98

U=a+(n-1)b
U7=a+(7-1)b
U5=a+(5-1)b
33=a+6b
23=a+4b
dieliminasi
10=2b
b=5

contoh:U5=23
23=a+4*5
23=a+20
a=3

U20=3+19.5
=3+95
=98