Cho dãy (un) xác định bởi công thức truy hồi:
Số hạng tổng quát của dãy là
A. un = 2n - 3.
B. un = 2n + 1 + 3.
C. un = 2n + 1 - 3.
D. un = 2n + 3.

Cho dãy số (un) với : un=7-2n
Khẳng định sai là
A. 3 số hạng đầu của dãy: u1=5, u2=3, u3=1.
B. Số hạng thứ n+1:un+1=8-2n.
C. Là cấp số cộng có d=-2.
D. Số hạng thứ 4: u4=-1.

Cho dãy số có các số hạng đầu là: -2; 0; 2; 4; 6;...
Số hạng tổng quát của số hạng này có dạng:
A. un=-2n.
B. un=(-2)+n.
C. un=(-2)(n+1).
D. un=(-2)+2(n-1).

Cho dãy só có các số hạng đầu là: 8, 15, 22, 29, 36, ...
Số hạng tổng quát của số hạng này là:
A. un=7n+7.
B. un=7n.
C. un=7n+1.
D. un: không viết được dưới dạng công thức.

A.
B.
C.
D.

Choose one sentence that has the same meaning to the root one:
No sooner had she put the telephone down than her boss rang back.
A. As soon as her boss rang back, she put down the telephone.
B. Scarcely had she put the telephone down when her boss rang back.
C. Hardly she had hung up, she rang her boss immediately.
D. She had hardly put the telephone down without her boss rang back.

Choose one sentence that has the same meaning as the root one:
There was a hurricane in August 1992 over West Africa. This hurricane was named Andrew.
A. There was a hurricane who was named Andrew in August 1992 over West Africa. 
B. There was a hurricane what was named Andrew in August 1992 over West Africa.
C. There was a hurricane which was named Andrew in August 1992 over West Africa.
D. There was a hurricane whom was named Andrew in August 1992 over West Africa.

Choose one sentence that has the same meaning as the root one:
Whatever has been ordered will be delivered.
A. We will be delivered anything that ordered.
B. We will delivered something that was ordered.
C. We will deliver everything that has been ordered.
D. We will be delivered nothing that had ordered.

Choose one sentence that has the same meaning as the root one:
John said, “You’d better not lend them any money, Mary.”
A. John said Mary not to lend them any money.
B. John said to Mary not lend them any money.
C. John advised Mary should not lend them any money.
D. John advised Mary not to lend them any money.

Choose one sentence that has the same meaning as the root one:
Were it not for the money, this job wouldn't be worthwhile.
A. The only thing that makes this job worthwhile is the money.
B. This job is rewarding at all.
C. This job offers a poor salary.
D. Although the salary is poor, the job is worthwhile.