Câu hỏi đâu em ơi

6) \(=3\left(x-y\right)\left(1-2a\right)\)

7) \(=\left(x+2\right)\left(5+8y\right)\)

8) \(=3x\left(x-1\right)+6y\left(x-1\right)=3\left(x-1\right)\left(x+2y\right)\)

9) \(=2\left(2x-1\right)\left(2x+3\right)\)

10) \(=3x\left(x+3\right)\left(x-2\right)\)

1. 4x² - 4x 

= 4x(x - 1)

2. 3ax + 12x - 9

= 3(ax + 4x - 3)

3. 6xy + 2xy² - 8x²

= 2x(3y + y² - 4x)

4. -4ay + 10a - 8a²y

= -2a(2y - 5 + 8ay)

5. 10x³ - 8ax²

= 2x²(5x - 4a)

6. 3(x - y) - 6a(x - y)

= (3 - 6a)(x - y)

= 3(1 - 2a)(x - y)

7. 5(x + 2) + 8y(x + 2)

= (5 + 8y)(x + 2)

8. 3x(x - 1) - 6y(1 - x)

= 3x(x - 1) + 6y(x - 1)

= (3x + 6y)(x - 1)

= 3(x + 2y)(x - 1)

9. 4x(2x - 1) + 6(2x - 1)

= (4x + 6)(2x - 1)

= 2(2x + 3)(2x - 1)

10. 3x²(x + 3) - 6x(3 + x)

= 3x²(x + 3) - 6x(x + 3)

= (3x² - 6x)(x + 3)

= 3x(x - 2)(x + 3)

Bài 9:

6: \(\Leftrightarrow x+\dfrac{4}{3}-\dfrac{12}{5}=\dfrac{5}{2}-\dfrac{1}{4}+\dfrac{7}{8}=\dfrac{20-2+7}{8}=\dfrac{25}{8}\)

=>x=25/8-4/3+12/5=503/120

7: \(\Leftrightarrow\dfrac{1}{7}-\dfrac{1}{5}+x-\dfrac{3}{2}=\dfrac{16}{70}-\dfrac{9}{70}=\dfrac{1}{10}\)

=>x=1/10-1/7+1/5+3/2=58/35

8: \(\Leftrightarrow\dfrac{5}{4}-x+\dfrac{1}{5}-\dfrac{19}{20}=1-\dfrac{1}{2}+\dfrac{7}{10}=\dfrac{6}{5}\)

=>1/2-x=6/5

=>x=1/2-6/5=-7/10

9: \(\Leftrightarrow5-\dfrac{1}{3}+\dfrac{17}{4}-x=1+\dfrac{2-11}{12}=1-\dfrac{9}{12}=\dfrac{1}{4}\)

=>x=14/3+4=26/3

10: \(\Leftrightarrow\dfrac{-1}{12}+x-\dfrac{5}{12}=3-\dfrac{7}{6}+\dfrac{1}{2}\)

=>x-1/2=11/6+1/2

=>x=11/6+1=17/6

\(#nKaizz\)

`9,`

`6, 1 1/3 - 2 2/5 + x= 5/2 - (1/4 - 7/8)`

`4/3 -12/5 + x = 5/2 - (-5/8)`

`4/3 - 12/5 + x=25/8`

`-16/15 + x=25/8`

`x=25/8 - (-16/15)`

`x=25/8 + 16/15 = 503/120`

`7, 1/7 - (1/5 - x + 1 1/2)= 8/35 - 9/70`

`1/7 - (1/5 - x + 3/2)= 1/10`

`1/5 - x + 3/2 = 1/7 -1/10`

`1/5 -x + 3/2 = 3/70`

`1/5 -x=3/70 - 3/2`

`1/5-x=-51/35`

`x=1/5 - (-51/35)`

`x=1/5 + 51/35 = 58/35`

`8, 5/4 - x +(1/5 - 19/20)= 1- (1/2 - 7/10)`

`5/4 - x+ -3/4 = 1- (-1/5)`

`5/4 - x+ -3/4 = 6/5`

`5/4 - x=6/5 - (-3/4)`

`5/4 - x=39/20`

`x=5/4 - 39/20`

`x=-7/10`

`9, 5- (1/3 - 4 1/4+x) = 1+ (1/6 - 11/12)`

`5- (1/3- 4 1/4+x)=1+ -3/4 `

`5- (1/3 - 4 1/4+x) = 1/4`

`1/3- 4 1/4 +x=5-1/4`

`-47/12 +x=19/4`

`x=19/4 - (-47/12)`

`x=26/3`

`10, 1/4 - (1/3-x+5/12)=3-(1 1/6 - 1/2)`

`1/4-(1/3-x+5/12)=3-2/3`

`1/4 - (1/3-x+5/12) =7/3`

`1/3 - x+5/12 = 1/4 - 7/3`

`1/3-x+5/12 = -25/12`

`1/3-x = (-25/12)-5/12`

`1/3-x = -5/2`

`x=1/3 - (-5/2)`

`x=17/6`

Em đăng ký tham gia cuộc thi này

Em đăng ký tham gia cuộc thi này

Bài 5:

a: \(A=\frac{-3\left(x+1\right)}{x^2-x-6}\)

\(=\frac{-3\left(x+1\right)}{x^2-3x+2x-6}\)

\(=\frac{-3\left(x+1\right)}{\left(x-3\right)\left(x+2\right)}\)

\(x^2-4=0\)

=>(x-2)(x+2)=0

=>x=2(nhận) hoặc x=-2(loại)

Khi x=2 thì \(A=\frac{-3\cdot\left(2+1\right)}{\left(2-3\right)\left(2+2\right)}=\frac{-3\cdot3}{\left(-1\right)\cdot4}=\frac94\)

b: \(B=\frac{2x}{x+3}-\frac{x}{3-x}-\frac{3x^2+9}{x^2-9}\)

\(=\frac{2x}{x+3}+\frac{x}{x-3}-\frac{3x^2+9}{\left(x-3\right)\left(x+3\right)}\)

\(=\frac{2x\left(x-3\right)+x\left(x+3\right)-3x^2-9}{\left(x-3\right)\left(x+3\right)}=\frac{2x^2-6x+x^2+3x-3x^2-9}{\left(x-3\right)\left(x+3\right)}\)

\(=\frac{-3x-9}{\left(x-3\right)\left(x+3\right)}=\frac{-3\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}=\frac{-3}{x-3}\)

c: P=B:A

\(=-\frac{3}{x-3}:\frac{-3\left(x+1\right)}{\left(x-3\right)\left(x+2\right)}\)

\(=\frac{3}{x-3}\cdot\frac{\left(x-3\right)\left(x+2\right)}{3\left(x+1\right)}=\frac{x+2}{x+1}\)

Để P nguyên thì x+2⋮x+1

=>x+1+1⋮x+1

=>1⋮x+1

=>x+1∈{1;-1}

=>x∈{0;-2}

mà x là số tự nhiên

nên x=0

Bài 2: 

a: Ta có: ΔABC cân tại A

mà AH là đường cao

nên AH là tia phân giác của góc BAC

b: Xét ΔAMH vuông tại M và ΔANH vuông tại N có

AH chung

\(\widehat{MAH}=\widehat{NAH}\)

Do đó: ΔAMH=ΔANH

Suy ra: AM=AN

hay ΔAMN cân tại A

c: Xét ΔABC có AM/AB=AN/AC

nên MN//BC

d: \(AH^2-AN^2=HN^2\)

\(BH^2-BM^2=MH^2\)

mà HN=MH

nên \(AH^2-AN^2=BH^2-BM^2\)

hay \(AH^2+BM^2=BH^2+AN^2\)

Vẽ hình giúp e đc ko ạ

Bài 2: Chọn C

Bài 4: 

a: \(\widehat{C}=180^0-80^0-50^0=50^0\)

Xét ΔABC có \(\widehat{A}=\widehat{C}< \widehat{B}\)

nên BC=AB<AC

b: Xét ΔABC có AB<BC<AC

nên \(\widehat{C}< \widehat{A}< \widehat{B}\)