1: ĐKXĐ: x<>1/2

Ta có: \(\frac{2x-1}{4}=\frac{4}{2x-1}\)

=>\(\left(2x-1\right)\left(2x-1\right)=4\cdot4\)

=>\(\left(2x-1\right)^2=16\)

=>\(\left[\begin{array}{l}2x-1=4\\ 2x-1=-4\end{array}\right.\Rightarrow\left[\begin{array}{l}2x=4+1=5\\ 2x=-4+1=-3\end{array}\right.\Rightarrow\left[\begin{array}{l}x=\frac52\left(nhận\right)\\ x=-\frac32\left(nhận\right)\end{array}\right.\)

2: ĐKXĐ: x<>1/2

\(\frac{2x-1}{27}=\frac{3}{2x-1}\)

=>\(\left(2x-1\right)\left(2x-1\right)=27\cdot3=81\)

=>\(\left(2x-1\right)^2=81\)

=>\(\left[\begin{array}{l}2x-1=9\\ 2x-1=-9\end{array}\right.\Rightarrow\left[\begin{array}{l}2x=10\\ 2x=-8\end{array}\right.\Rightarrow\left[\begin{array}{l}x=5\left(nhận\right)\\ x=-4\left(nhận\right)\end{array}\right.\)

3: ĐKXĐ: x∉{0;-1}

Ta có: \(\frac{4}{x}=\frac{8}{x+1}\)

=>\(\frac{1}{x}=\frac{2}{x+1}\)

=>2x=x+1

=>2x-x=1

=>x=1(nhận)

4: ĐKXĐ: x<>-5

Ta có: \(\frac{x-1}{x+5}=\frac67\)

=>7(x-1)=6(x+5)

=>7x-7=6x+30

=>7x-6x=7+30

=>x=37(nhận)

5: \(\frac{x-3}{5}=\frac{5-2x}{11}\)

=>11(x-3)=5(5-2x)

=>11x-33=25-10x

=>21x=25+33=58

=>\(x=\frac{58}{21}\)

6: ĐKXĐ: x∉{-1;-7}

Ta có: \(\frac{x}{x+1}=\frac{x+5}{x+7}\)

=>x(x+7)=(x+1)(x+5)

=>\(x^2+7x=x^2+6x+5\)

=>7x=6x+5

=>7x-6x=5

=>x=5(nhận)

7: ĐKXĐ: x∉{-2/5;-1/5}

ta có: \(\frac{2x+3}{5x+2}=\frac{4x+5}{10x+2}\)

=>(2x+3)(10x+2)=(5x+2)(4x+5)

=>\(20x^2+4x+30x+6=20x^2+25x+8x+10\)

=>34x+6=33x+10

=>34x-33x=10-6

=>x=4(nhận)

8: ĐKXĐ: x∉{-2;-8}

ta có: \(\frac{2x-18}{2x+4}=\frac{2x-17}{2x+16}\)

=>\(\frac{2\left(x-9\right)}{2\left(x+2\right)}=\frac{2x-17}{2x+16}\)

=>\(\frac{x-9}{x+2}=\frac{2x-17}{2x+16}\)

=>(2x-17)(x+2)=(x-9)(2x+16)

=>\(2x^2+4x-17x-34=2x^2+16x-9x-144\)

=>-13x-34=7x-144

=>-13x-7x=-144+34

=>-20x=-110

=>\(x=\frac{110}{20}=\frac{11}{2}\) (nhận)

tất cả các câu đều là tỉ lệ thức nhé

a: ta có: m⊥d

n⊥d

Do đó: m//n

b: Ta có: m//n

=>\(\hat{A_3}+\hat{B_1}=180^0\) (hai góc trong cùng phía)

=>\(\frac12\cdot\hat{B_1}+\hat{B_1}=180^0\)

=>\(\frac32\cdot\hat{B_1}=180^0\)

=>\(\hat{B_1}=180^0:\frac32=120^0\)

=>\(\hat{A_3}=120^0\cdot\frac12=60^0\)

Ta có: \(\hat{B_1}+\hat{B_2}=180^0\) (hai góc kề bù)

=>\(\hat{B_2}=180^0-120^0=60^0\)

c: Qua E, kẻ tia EF nằm giữa hai tia EA và EC sao cho EF//Am//Cn

Ta có: EF//Am

=>\(\hat{AEF}=\hat{EAm}=60^0\)

Ta có: EF//CB

=>\(\hat{FEC}=\hat{ECB}=80^0\)

Ta có: tia EF nằm giữa hai tia EA và EC

=>\(\hat{AEC}=\hat{AEF}+\hat{CEF}=60^0+80^0=140^0\)

Bài 1:

a: \(M=\frac13xy\left(-\frac12xy^2z^3\right)^2\cdot x^3y\)

\(=\frac13x^4y^2\cdot\frac14x^2y^4z^6\)

\(=\left(\frac13\cdot\frac14\right)\cdot\left(x^4\cdot x^2\right)\cdot\left(y^4\cdot y^2\right)\cdot z^6=\frac{1}{12}x^6y^6z^6\)

Bậc là 6+6+6=18

Hệ số là 1/12

Phần biến là \(x^6;y^6;z^6\)

b: \(M=\frac{1}{12}x^6y^6z^6=\frac{1}{12}\cdot\left(xyz\right)^6\)

Thay x=-4;y=0,5;z=-0,5 vào M, ta được:

\(M=\frac{1}{12}\cdot\left\lbrack-4\cdot0,5\cdot\left(-0,5\right)\right\rbrack^6=\frac{1}{12}\cdot\left(2\cdot0,5\right)^6=\frac{1}{12}\)

Bài 2:

a: \(\left(xy^2-6x^2y\right)-\left(-2xy^2-5x^2y\right)+\left(x^2y-6xy^2\right)\)

\(=xy^2-6x^2y+2xy^2+5x^2y+x^2y-6xy^2=-3xy^2\)

b: \(N=\left(15x^5y^4-20x^3y^2+5x^2y^3\right):5x^2y\)

\(=\frac{15x^5y^4}{5x^2y}-\frac{20x^3y^2}{5x^2y}+\frac{5x^2y^3}{5x^2y}=3x^3y^3-4xy+y^2\)

Thay x=1;y=1 vào N, ta được:

\(N=3\cdot1^3\cdot1^3-4\cdot1\cdot1+1^2\)

=3-4+1

=0

c: \(\left(3x^2-x-3\right)-2x\left(x+2\right)-\left(x+4\right)\left(x-5\right)=1\)

=>\(3x^2-x-3-2x^2-4x-\left(x^2-x-20\right)=1\)

=>\(x^2-5x-3-x^2+x+20=1\)

=>-4x+17=1

=>-4x=-16

=>x=4

ẩn danh thì chịu