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Kelas : IX SMP
Bab : Barisan dan deret
Pembahasan :
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
Matematika SMP Kelas VII
-100 - 99 - 98 - ... - 1 + 0 + 1 + ...49 + 50 = ?
-50 + 50 = 0
-49 + 49 = 0
.
.
-1 + 1 = 0
sisa = -100 - 99 - 98 - .. - 51 = ?
-100
-99 - 51 = -150
- 98 - 52 = -150
.
-76 - 74 = - 150
-75
seluruh = (-76 sampai -80) + (-81 sampai -90) + (-91 sampai -99) + (-100) + -75
seluruh = (5 x (-150)) + (10 x (-150)) + (9 x (-150)) - 100 - 75
seluruh= -750 - 1.500 - 1.350 - 175
seluruh = -3.775