Choose the correct answer

When did you go to the zoo? I ___________ there yesterday.

a. go

b. went

c. goes

d. was

Rút gọn các biểu thức sau:

a ) a b + a b + a b b a   v ớ i > 0   v à b>0 b > b ) $ m 1 − 2 x + x 2 ⋅ 4 m − 8 m x + 4 m x 2 81   v ớ i   m > 0 v à  x ≠ 1