Ta có: \(3x=7y\)

\(\Rightarrow\frac{x}{7}=\frac{y}{3}=\frac{y-x}{3-7}=\frac{8}{-4}=-2\)

\(\Rightarrow\hept{\begin{cases}x=-14\\y=-6\end{cases}}\)

\(\frac{x+2}{3}=\frac{y-1}{4}=\frac{z+3}{5}\)

\(=\frac{x+2-y+1+z+3}{3-4+5}\)

\(=\frac{x-y+z+6}{4}=\frac{66}{4}=16,5\)

\(\Rightarrow x,y,z=....\)

\(3^{x-1}+\frac{5}{3}.3^x=162\)

\(\Leftrightarrow3^x.\frac{1}{3}+\frac{5}{3}.3^x=162\)

\(\Leftrightarrow3^x.2=162\)

\(\Leftrightarrow3^x=81\Leftrightarrow x=4\)

Bài 1: Tính hợp lí:

\(a)\)\(\frac{14}{57}+\frac{29}{23}-\frac{71}{57}+\frac{-6}{23}\)

\(=\)\(\left(\frac{14}{57}-\frac{71}{57}\right)+\left(\frac{29}{23}+\frac{-6}{23}\right)\)

\(=\)\(\left(-\frac{57}{57}\right)+\left(\frac{23}{23}\right)\)

\(=\)\(\left(-1\right)+1\)

\(=\)\(0\)

\(b)\)\(\frac{5}{12}.\left(\frac{-3}{4}\right)+\frac{7}{12}.\left(\frac{-3}{4}\right)\)

\(=\)\(\left(\frac{-3}{4}\right).\left(\frac{5}{12}+\frac{7}{12}\right)\)

\(=\)\(\left(\frac{-3}{4}\right).1\)

\(=\)\(-\frac{3}{4}\)

\(c)\)\(\left(\frac{-3}{11}\div\frac{5}{22}\right).\left(\frac{-15}{3}\div\frac{26}{3}\right)\)

\(=\)\(\left(\frac{-3}{11}.\frac{22}{5}\right).\left(\frac{-15}{3}.\frac{3}{26}\right)\)

\(=\)\(\frac{-6}{5}.\frac{-15}{26}\)

\(=\)\(\frac{9}{13}\)

\(d)\)\(\left(0,25\right)^{100}.4^{103}\)

\(=\)\(\left(\frac{1}{4}\right)^{100}.4^{103}\)

\(=\)\(\left(\frac{1}{4}.4\right)^{100+103}\)

\(=\)\(1^{203}\)

\(=\)\(1\)

Bài 2: Tìm x, biết:

\(a)\)\(\left(\frac{3}{7}-2x\right)^2=\frac{4}{9}\)

\(\Leftrightarrow\)\(\left(\frac{3}{7}-2x\right)^2=\left(\frac{2}{3}\right)^2\)

\(\Leftrightarrow\)\(\frac{3}{7}-2x=\frac{2}{3}\)

\(\Leftrightarrow\)\(2x=\frac{3}{7}-\frac{2}{3}\)

\(\Leftrightarrow\)\(2x=\frac{-5}{21}\)

\(\Leftrightarrow\)\(x=\frac{-5}{21}\div2\)

\(\Leftrightarrow\)\(x=\frac{-5}{42}\)

\(b)\)\(x+5,5=7,5\)

\(\Leftrightarrow\)\(x=7,5-5,5\)

\(\Leftrightarrow\)\(x=2\)

Choose the word whose main stress pattern is placed differently from the others:

1. A. party                       B. favourite                        C. delicious                     D. comfortable

2. A. appear                     B. birthday                       C. invite                          D. behind    

3. A. address                   B. nervous                        C. thirty                          D. telephone

4. A. invite                      B. directory                      C. personal                      D. address

5. A. information            B. invitation                     C. birthday                      D. engineer

6. A. awful                      B. empty                          C. amazing                      D. comfortable

7. A. apartment               B. amazing                       C. complain                    D. factory

8. A. delicious                 B. terrible                         C. lovely                         D. favourite

III. Choose the best answer a, b, c, or d to complete the sentence.

1.   My father can make beautiful pieces of art ________ empty eggshells.

a. of                            b. from                       c. in                             d. into

2.   Why don’t you take ________ a new hobby?           

a. up                            b. in                            c. over                        d. after

3.   Collecting cars is a(n) ________ hobby. It costs a lot of money.   

a. interesting             b. cheap                     c. expensive              d. unusual

4.   More people are ________ birds today than ever before.   

a. seeing                     b. looking                  c. hearing                   d. watching

5.   Do you enjoy ________ board games?          

a. play                        b. to play                    c. playing                   d. played

6.   Be careful not to drop it; it’s very ________.

a. unique                    b. fragile                    c. difficult                  d. unusual

7.   Sam and I ________ the same hobby. We both playing computer games.

a. share                       b. play                        c. do                            d. work

8.   I hope he’ll teach me ________ to do eggshell carving.     

a. what                        b. where                     c. how                         d. when

9.   ________ have you had your hobby? ~ For three years.     

a. How much             b. How long               c. How often             d. When

10. ‘I think model making is an expensive hobby.’ ‘________ it’s incredibly cheap.’

a. You’re right          b. Certainly               c. No matter              d. Not at all

TL:

5^x+2. 4^y = 50^x

= 5³ . 4¹ = 50¹

=  ( 5³ . 4¹ ) : 50

= 6550 : 50

= 131

TL

5^x+2. 4^y = 50^x

= 131

HT

11 . D

12 . C

13 . A

14 . C

15 . A

16 . C

1`7 . A

TL

11. D

12. C

13. A

14. C

15. A

16. C

17. C

HT

6 . A

7 . C

8 . A

9 . C

10 . B

6.A

7.C

8.A

9.C

10.B