Ta luôn có \(a^2+b^2-2ab=\left(a-b\right)^2\)

Áp dụng hằng đẳng thức trên thì có :

\(\left(2x+3\right)^2+\left(2x+5\right)^2-2\left(2x+3\right)\left(2x+5\right)\)

\(=\left[\left(2x+5\right)-\left(2x+3\right)\right]^2\)

\(=2^2\)

\(=4\)

\(=\frac{90-90.3+90.6}{90.4-90.12+90.24}=\frac{90.\left(1-3+6\right)}{90\left(4-12+24\right)}=\frac{4}{16}=\frac{1}{4}\)

7,1;7,5;17,0;1000,0

Bi' qua'

(11-12) Choose the underlined word or phrase(A,B,C, or D) that needs correcting:

11/ If you go to a language school, you should try speaking English as much as possible.

12 We can stop adding on the problem while scientists look for the answers.

(13-16) Use the correct tense or form of the verbs in parentheses.

13/ We __________ English for four years . (learn)

14/ I wish I____________ a good time tomorrow . ( have)

15/ Do you enjoy __________ on the internet. ( chat)

16/ malaysia ___________ into two regions. (divide)

17-22) Use the correct form of the words in parentheses:

17/ Today there is a meeting of local ___________ . (conserve)

18/ The problem, __________to say, is the cost involved. ( need)

19/ The use of light and dark __________ good and evil. ( symbol)

20/ They put an ___________ in the newspaper to sell their house. (advertise)

21/ She likes living _________ in a village . ( peace)

22/ The hotel is _________ located far from the downtown area. (convenience

(11-12) Choose the underlined word or phrase(A,B,C, or D) that needs correcting:

11/ A lot of new schools were built recently.

12 / Environmental pollution is one of the most serious problems faced mankind today.

(13-16) Use the correct tense or form of the verbs in parentheses.

13/ Mr. Green always __________ to work by car last year . (go)

14/ She wishes her parents ____________ here now . ( be)

15/ This magazine__________ widely __________ by both teenagers and adults. ( read)

16/ If you study hard, you ___________ the final exam. (pass)

17-22) Use the correct form of the words in parentheses:

17/ Most accidents can be avoided if people pay more ___________ . ( attend)

18/ The fans were extremely __________ because their team lost. ( appoint)

19/ Ha Long Bay attracts large numbers of __________ . ( sightsee)

20/ Going abroad for studying is becoming ___________ popular nowadays. (increase)

21/ She enjoys _________ with her classmates. ( picnic)

22/ Her parents always _________ her to study harder. (courage)

1 500 000 đ