M = 1 + 2 + 3 + 4 + ... + (n - 3) + (n - 2) + (n - 1) + n

\(M=\frac{n\left(n+1\right)}{2}\)

TA có

kết quả là:

3 x 1

= 3

( theo bảng cửu chương 3 )

a) a^x = 1

=> a = 1

b) a^x = 0

=> a = 0

nha bn

tại sao sai

mới lớp 6 ak

all of us were ........ that he was successful in the final exam (surprise)

towns which attract ......... are usually crowded in the summer(tour)

Ba was ..... ill right after eating those mushrooms(serious)

it is ...... in Britain to eat turkeys at Christmas

chia dạng đúng của từ trong ngoặc