tolong yg bisa tolong bntu saya,tlong bntu dengan caranya terimakasih❤

▶50 suku
A = 2 + 4 + 6 + ... + 100
A = 100 + 98 + ... + 4 + 2
----------------------------------- ( + )
2A = 102 + 102 + ... + 102
2A = 102 × 50
A = 102 × 50/2
A = 51 × 50
A = 2550

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

▶
-100 - 99 - 98 - ... - 1 + 0 + 1 + ... + 99
= -100 + (-99 + 99) + ... + (-1 + 1)
= -100 + 0 + ... + 0
= -100