1 Where are the picture which were on this wall

2 My father is the person who has great influence on my behavior

3 Do you like the flowers which I bought this morning?

4 All of us are interested in the man who is teaching us PE

5 What's the name of the girl who lent you this book?

6 I don't know the man who wrote lots of good books

7 The girl who has worked here for 5 days will leave me the message

8 All the man who are businessman attended the meeting

9 Do you know the lady who is presenting the topic

10 I haven't read the novel which was written by Nam cao

vì đưởng thẳng c đi qua a và b tạo thành 2 cặp góc vuông bằng nhau

⇒ a//b

b) Do B1 và A1 ở vị trí trong cùng phía : 

=>a1+b1=180 độ.

=>B1=180 độ - 120 độ

B1=60 độ

6.5:

a: 5⋮n+1

mà n+1>=1(do n là số tự nhiên)

nên n+1∈{1;5}

=>n∈{0;4}

b: 15⋮n+2

mà n+2>=2(do n là số tự nhiên)

nên n+2∈{3;5;15}

=>n∈{1;3;13}

6.4:

a: \(4=2^2;6=2\cdot3;8=2^3\)

Do đó: BCNN(4;6;8)\(=2^3\cdot3=24\)

x-1∈BC(4;6;8)

=>x-1∈B(24)

=>x-1∈{24;48;72;96;120;144;168;...}

=>x∈{25;49;73;97;121;145;169;...}

mà x<150

nên x∈{25;49;73;97;121;145}

b: \(8=2^3;15=3\cdot5;20=2^2\cdot5\)

Do đó: BCNN(8;15;20)\(=2^3\cdot3\cdot5=8\cdot15=120\)

x+1∈BC(8;15;20)

=>x+1∈B(120)

=>x+1∈{120;240;360;...}

=>x∈{119;239;359;...}

mà 0<x<=300

nên x∈{119;239}

c: \(24=2^3\cdot3;32=2^5;60=2^2\cdot5\cdot3\)

Do đó: ƯCLN(24;32;60)\(=2^2=4\)

x-5∈ƯC(24;32;60)

=>x-5∈Ư(4)

=>x-5∈{1;-1;2;-2;4;-4}

=>x∈{6;4;7;3;9;1}

mà x<20

nên x∈{6;4;7;3;9;1}

d: \(120=2^3\cdot3\cdot5;48=2^4\cdot3;72=2^3\cdot3^2\)

Do đó: ƯCLN(120;48;72)\(=2^3\cdot3=24\)

7-x∈ƯC(120;48;72)

=>7-x∈Ư(24)

=>x-7∈Ư(24)

=>x-7∈{1;-1;2;-2;3;-3;4;-4;6;-6;8;-8;12;-12;24;-24}

=>x∈{8;6;9;5;10;4;11;3;13;1;15;-1;19;-5;31;-17}

mà x là số tự nhiên

nên x∈{8;6;9;5;10;4;11;3;13;1;15;19;31}

Bài 6:

a: 17⋮x; 21⋮x; 51⋮x

=>x∈ƯC(17;21;51)

=>x∈Ư(1)

=>x=1

b:

\(48=2^4\cdot3;60=2^2\cdot3\cdot5\)

Do đó: ƯCLN(48;60)\(=2^2\cdot3=12\)

48⋮x; 60⋮x

=>x∈ƯC(48;60)

mà x lớn nhất

nên x=ƯCLN(48;60)

=>x=12

c:

\(12=2^2\cdot3;15=3\cdot5\)

Do đó: BCNN(12;15)\(=2^2\cdot3\cdot5=60\)

x⋮12; x⋮15

=>x∈BC(12;15)

mà x<65

nên x=60

d:

\(18=2\cdot3^2;24=2^3\cdot3\)

Do đó: BCNN(18;24)\(=2^3\cdot3^2=72\)

x⋮18

=>x∈B(18)

mà x∈B(24)

nên x∈BC(18;24)

=>x∈B(72)

mà x bé nhất

nên x=72

e:

\(39=13\cdot3;65=13\cdot5;91=13\cdot7\)

Do đó: BCNN(39;65;91)\(=13\cdot3\cdot5\cdot7=1365\)

x⋮39; x⋮65; x⋮91

=>x∈BC(39;65;91)

=>x∈B(1365)

mà 400<x<2600

nên x=1365

f:

\(36=2^2\cdot3^2;42=2\cdot3\cdot7\)

Do đó: ƯCLN(36;42)\(=2\cdot3=6\)

x∈Ư(36)

42⋮x nên x∈Ư(42)

=>x∈ƯC(36;42)

=>x∈Ư(6)

mà 3<x<15

nên x=6

19) Ta có: \(\sqrt[3]{x^3+9x^2}=x+3\)

\(\Leftrightarrow x^3+9x^2=\left(x+3\right)^3\)

\(\Leftrightarrow x^3+9x^2=x^3+9x^2+27x+27\)

\(\Leftrightarrow27x+27=0\)

\(\Leftrightarrow27x=-27\)

hay x=-1

Vậy: S={-1}

6) Ta có: \(\sqrt{9x^2-6x+1}-x=4\)

\(\Leftrightarrow\sqrt{\left(3x-1\right)^2}=x+4\)

\(\Leftrightarrow\left|3x-1\right|=x+4\)

\(\Leftrightarrow\left[{}\begin{matrix}3x-1=x+4\left(x\ge\dfrac{1}{3}\right)\\1-3x=x+4\left(x< \dfrac{1}{3}\right)\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}3x-x=4+1\\-3x-x=4-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=5\\-4x=3\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{2}\left(nhận\right)\\x=\dfrac{-3}{4}\left(nhận\right)\end{matrix}\right.\)

Vậy: \(S=\left\{\dfrac{5}{2};\dfrac{-3}{4}\right\}\)

8)

ĐKXĐ: \(x>2\)

Ta có: \(\sqrt{x^2+2x+4}=x-2\)

\(\Leftrightarrow x^2+2x+4=\left(x-2\right)^2\)

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

\(\Leftrightarrow6x=0\)

hay x=0(loại)

Vậy: \(S=\varnothing\)

9) Ta có: \(\sqrt{x^2-6x+9}=5\)

\(\Leftrightarrow\sqrt{\left(x-3\right)^2}=5\)

\(\Leftrightarrow\left|x-3\right|=5\)

\(\Leftrightarrow\left[{}\begin{matrix}x-3=5\\x-3=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=8\\x=-2\end{matrix}\right.\)

Vậy: S={8;-2}

Sửa đề: C={x∈N; a∈N*|x=4a+3; a<6}

a∈N*

mà a<6

nên a∈{1;2;3;4;5}

=>x∈{7;11;15;19;23]

=>C={(7;1);(11;2);(15;3);(19;4);(23;5)}

\(1-\frac{1}{3}-\frac{1}{9}=\frac{9}{9}-\frac{3}{9}-\frac{1}{9}=\frac{9-3-1}{9}=\frac{5}{9}\)

5/9 T I C K MÌNH NHÁ

a: a⊥c

b⊥c

Do đó: a//b

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