Question

Tentukan hasil dari ( tanpa menghitung satu persatu ) a. 1 + 3 + 5 + 7 + 9 + . . . . . + 99 b.1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + . . . . . . - 100 c. ( -100 ) - 99 - 98 - . . . . . - 2 - 1 - 0 + 1 + 2 + . . . . + 48 + 49 + 50

Answer 1

Verified answer

A.
a = 1
b = 3-1= 2
Banyak suku :
= 99/2
= 49,5 (50)

S50 :
= n/2 (a + Un)
= 50/2 (1 + 99)
= 25 x 100
= 2500

B.
1-2 = -1
3-4 = -1
.. - .. = -1
99-100 = -1

Banyak kali penjumlahan :
= 100/2
= 50

Maka hasilnya :
= 50 x (-1)
= -50

C.
A = -100
B = -99 - (-100) = 1
Banyak suku :
= 100 + 1 + 50
= 151

S151 :
= n/2 (a + Un)
= 151/2 (-100 + 50)
= 75,5 x -50
= -3775