Tentukan hasil dari ( tanpa menghitung satu persatu) A. 2+4+6+8+10+.......+100 B. -1+2-3+4-5+6-7+8-........+100 C.-100-99-98-......-2-1-0+1+2+.......+97+98

A.
2 + 4 + 6 + ... + 100 ---> 50 suku
= (2 + 98) + (4 + 96) + ... + (48 + 52) + 50 + 100
= (100 + 100 + ... + 100) + 50 + 100
= (100 × 48/2) + 150
= 2400 + 150
= 2550

B.
(-1 + 2) + (-3 + 4) + ... + (-99 + 100) ---> 100 suku
= (1) × 100/2
= 50

C.
-100 - 99 - 98 - ... - 1 + 0 + 1 + ... + 97 + 98
= -100 - 99 + (-98 + 98) + ... + (-1 + 1)
= -100 - 99 + 0 + 0 + ... + 0
= -199