I/ 1C 2C 3B 4D 5d

II/ 1c 2a 3d 4b

I:

1.D    2.D  3.B   4.D   5.D

II:

1.C   2.C   3.D   4.A

Bài 2: Số công nhân lúc sau là 150-100=50(người)

Thời gian hoàn thành là:

\(150\cdot36:50=3\cdot50=150\) (ngày)

Bài 1:

a: Hệ số tỉ lệ là: \(k=x\cdot y=2\cdot\left(-3\right)=-6\)

b: xy=-6

=>\(y=-\frac{6}{x}\)

c: Khi x=5 thì \(y=-\frac65=-1,2\)

Khi x=-4/7 thì \(y=-6:\frac{-4}{7}=6\cdot\frac74=\frac{42}{4}=\frac{21}{2}\)

d: \(y=\frac23\)

=>\(x\cdot\frac23=-6\)

=>\(x=-6:\frac23=-6\cdot\frac32=-9\)

C

c

B-A-B-D-A-D-D-C-B-C

b: \(\frac{6n-2}{3n+1}\) là số nguyên

=>6n-2⋮3n+1

=>6n+2-4⋮3n+1

=>-4⋮3n+1

=>3n+1∈{1;-1;2;-2;4;-4}

=>3n∈{0;-2;1;-3;3;-5}

mà 3n⋮3(n∈Z)

nen 3n∈{0;-3;3}

=>n∈{0;-1;1}

c: \(\frac{n^2-3n+5}{n-2}\) là số nguyên

=>\(\frac{n^2-2n-n+2+3}{n-2}\) là số nguyên

=>\(\frac{3}{n-2}\) là số nguyên

=>n-2∈{1;-1;3;-3}

=>n∈{3;1;5;-1}

\(\Rightarrow x=\dfrac{5}{12}-\dfrac{1}{4}=\dfrac{1}{6}\)

\(0,25+x=\dfrac{5}{12}\Rightarrow\dfrac{1}{4}+x=\dfrac{5}{12}\)

\(\Rightarrow x=\dfrac{5}{12}-\dfrac{1}{4}=\dfrac{5-1.3}{12}=\dfrac{2}{12}=\dfrac{1}{6}\)

\(a,\left(2x-1\right)^2-25=0.\\ \Leftrightarrow\left(2x-1\right)^2=25.\\ \Leftrightarrow\left[{}\begin{matrix}2x-1=5.\\2x-1=-5.\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3.\\x=-2.\end{matrix}\right.\) 

\(b,\left(x-3\right)\left(5-2x\right)=0.\\ \Leftrightarrow\left[{}\begin{matrix}x-3=0.\\5-2x=0.\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3.\\x=\dfrac{5}{2}.\end{matrix}\right.\)

\(c,\dfrac{x+1}{x-2}+\dfrac{x-1}{x+2}-\dfrac{2\left(x^2+2\right)}{x^2-4}=0.\)

\(\left(x\ne\pm2\right).\)

\(\Leftrightarrow\dfrac{\left(x+1\right)\left(x+2\right)+\left(x-1\right)\left(x-2\right)-2x^2-4}{\left(x-2\right)\left(x+2\right)}=0.\)

\(\Rightarrow\left(x+1\right)\left(x+2\right)+\left(x-1\right)\left(x-2\right)-2x^2-4=0.\)

\(\Leftrightarrow x^2+3x+2+x^2-3x+2-2x^2-4=0.\)

\(\Leftrightarrow0=0\) (luôn đúng).

\(\dfrac{6}{5}\)

6/5

26 different

27 pronunciation

28 comfortable

29 performers

30 windy

31 unhealthy

32 childhood

33 

34 flight

35 suddenly

IV.

26. different

27. pronunciation

28. comfortable

29. performers

30. windy

31. unhealthy

32. childhood

33. successfully

34. flights

35. suddenly