Để phân thức A=\(\frac{2x-1}{x^2-x}=\frac{2x-1}{x\left(x-1\right)}\) được xác định thì

\(\Leftrightarrow\) x²-x\(\ne\) 0\(\Leftrightarrow\) x(x-1)\(\ne\) 0

\(\Leftrightarrow\) x=0;1

b.

Tại x=0 thì phân A có giá trị là \(\frac{2x-1}{x\left(x-1\right)}\)=\(\varnothing\)

Tại x=3 thì phân thức có giá trị là \(\frac{2x-1}{x\left(x-1\right)}\) =\(\frac{2\times3-1}{3\times\left(3-1\right)}=\frac{5}{6}\)

x =49 \(\Leftrightarrow\) \(\sqrt{x}\) =7

A(x)=3x³-2x²+x-a⋮x-3 thì dư -a+66

Để 3x³-2x²+x-a chia hết cho x-3 thì dư phải =0 \(\Rightarrow\) -a+66=0\(\Leftrightarrow\) a=66

A=\(\frac{5x+6}{4-x^2}+\frac{4}{x+2}+\frac{2}{x-2}\)

để đkxd phân thức A thì A\(\ne0\)

\(\Leftrightarrow\) x\(\ne2,-2\)

A=\(\frac{5x+6}{4-x^2}+\frac{4}{x+2}+\frac{2}{x-2}\)

=\(\frac{-5x-6}{\left(x+2\right)\left(x-2\right)}+\frac{6}{x+2}\)

=\(\frac{-5x-6+6x-12}{\left(x+2\right)\left(x-2\right)}=\frac{-5x-6+6\left(x-2\right)}{\left(x+2\right)\left(x-2\right)}=\)

=\(\frac{-5x}{x+2}\)

Tại x=1 thì phân thức A sẽ bằng \(\frac{-5x}{x+2}\)

=\(\frac{-5.1}{1+2}=\frac{-5}{3}\)

Tại x=3 thì phân thức A sẽ bằng \(\frac{-5x}{x+2}\)

=\(\frac{-5.3}{3+2}=\frac{-15}{5}=\frac{-3}{1}=-3\)

1.Sam....played....(play) his guitar at half past seven last night

2. ...did......you...drive.....(drive) to work when the accidient happened?

3.It.....rained....(rain) on Monday so we didn't play football

4.At 6 o'clock on Saturday morning we..are traveling......(travel) to the airport

5.I...did 't lisen.....(not listen) to my teacher when he asked a question

6.In 1986 my father....lived....(live) in Paris.That's where he met my mother

7.What...did....they...do....(do) when you arrived?

8.Greg....did ' t study.....(not study) for the test we went to his place

9. ....did.....Caroline.....skied..(ski) when she broke her leg?

10.My parents..did't sleeped.....(not sleep) when I came home last night

I am sure

1. have_You ever ( do ) ___done_______ volunteer work ?

2. Yes. I ( do ) __did_______ volunteer work last month .

3. I ( collect ) __have collected_______ hundreds of old books and clothes for street children so far.

4. My sister wants to raise funds for street children so the ( make ) ____makes____ hundreds of postcards to sell them.

5. My hobby is carving eggshells and now I ( carve ) __am carving________ nearly 100.

6. Going home from school yesterday, I ( help ) __helped______ an old man to go across the street.

7. Last Tuesday, I ( go ) ____went_______ home late because there was a traffic jams near my school.

8. At Tet, my mother and her close friends often go to the hospitals to donate cakes, sweets and toys for the sick children there. She ( do ) _has done________ it for many years.

9. Lan never ( eat ) ____has eaten______ Banh tet . She will try some this year .

10. Linh is my close friend. We ( know ) ___have ___known______ each other for 5 years.

I don 't know

gọi 3đội máy cày lần lượt là a,b,c

theo đề bài ta có : \(\frac{a}{\frac{1}{2}}=\frac{b}{\frac{1}{3}}=\frac{c}{\frac{1}{4}}\)

Áp dụng tính chất dãy tỉ số bằng nhau :

\(\frac{b}{\frac{1}{3}}=\frac{c}{\frac{1}{4}}=\frac{b-c}{\frac{1}{3}-\frac{1}{4}}=\frac{3}{\frac{1}{12}}=\frac{1}{4}\)

suy ra :\(\frac{b}{\frac{1}{3}}=\frac{1}{4}\) \(\Leftrightarrow\) b=\(\frac{1}{12}\)

\(\frac{a}{\frac{1}{2}}\) =\(\frac{1}{4}\) \(\Leftrightarrow\) a=\(\frac{1}{8}\)

\(\frac{c}{\frac{1}{4}}\) =\(\frac{1}{4}\) \(\Leftrightarrow\) c=\(\frac{1}{16}\)

\(\left(\frac{2}{5}\right)^2.x=\left(\frac{2}{5}\right)^5\)

x=\(\left(\frac{2}{5}\right)^5\div\left(\frac{2}{5}\right)^2\)

x=\(\left(\frac{2}{5}\right)^{5-2}\)

x=\(\left(\frac{2}{5}\right)^3\)