Kelas : IX SMP
Bab : Barisan dan deret
Pembahasan :
Un = 2n – 1
99 = 2n – 1
2n = 100
n = 50
1 + 3 + 5 + 7 + … + 99 = n²
1 + 3 + 5 + 7 + … + 99 = 50²
1 + 3 + 5 + 7 + … + 99 = 2500
————————————————
1 – 2 + 3 – 4 + … – 100
= -1 – 1 – 1 – 1 – … – 1
= -(1 + 1 + … + 1)
= -(100/2)
= -50
————————————————
Un = 50
a + (n – 1)b = 50
-100 + n – 1 = 50
n – 101 = 50
n = 151
-100 – 99 – 98 – … + 50
= S151
= 151/2(-100 + 50)
= 151/2(-50)
= -3775
Originally posted 2022-06-05 10:09:39.