\(a,=2x^3-14x^2-6x\\ b,=-8x^4y^2+4xy^4-28x^2y^3\\ c,=-10x^5-15x^4+25x^3\\ d,=x^3-4x^2-2x^2+8x+3x-12=x^3-6x^2+11x-12\\ e,=10x^4+4x^3-15x^2-6x-5x-2=10x^4+4x^3-15x^2-11x-2\\ g,=6x-3-5x+15=x+12\)

\(\dfrac{1}{2}\times\dfrac{3}{4}:\dfrac{6}{5}=\dfrac{3}{8}:\dfrac{6}{5}=\dfrac{5}{16}\)

\(\dfrac{2}{3}+\dfrac{1}{6}:\dfrac{7}{12}=\dfrac{2}{3}+\dfrac{2}{7}=\dfrac{14}{21}+\dfrac{6}{21}=\dfrac{20}{21}\)

\(8\times\dfrac{3}{5}:\dfrac{12}{5}=\dfrac{24}{5}:\dfrac{12}{5}=2\)

\(\dfrac{4}{9}+\dfrac{3}{4}-\dfrac{1}{3}=\dfrac{16}{36}+\dfrac{27}{36}-\dfrac{12}{36}=\dfrac{31}{36}\)

a: \(=\dfrac{1}{2}\cdot\dfrac{3}{4}\cdot\dfrac{5}{6}=\dfrac{15}{48}=\dfrac{5}{16}\)

b: \(=\dfrac{2}{3}+\dfrac{12}{42}=\dfrac{2}{3}+\dfrac{2}{7}=\dfrac{20}{21}\)

c: \(=\dfrac{24}{5}\cdot\dfrac{5}{12}=2\)

d: \(=\dfrac{1}{9}+\dfrac{3}{4}=\dfrac{4+27}{36}=\dfrac{31}{36}\)

1: \(=\dfrac{3}{8}\cdot\dfrac{5}{6}=\dfrac{15}{24}=\dfrac{5}{8}\)

2: \(=\dfrac{2}{3}+\dfrac{12}{42}=\dfrac{2}{3}+\dfrac{2}{7}=\dfrac{14+6}{21}=\dfrac{20}{21}\)

3: \(=\dfrac{24}{5}\cdot\dfrac{5}{12}=2\)

4: \(=\dfrac{1}{3}+\dfrac{3}{4}=\dfrac{4+9}{12}=\dfrac{13}{12}\)

`1/2xx3/4:6/5= 1/2 xx 3/4 xx 5/6 = 3/8 xx 5/6 =5/16`           

`2/3+1/6:7/12 = 2/3 + 1/6 xx 12/7 = 2/3 + 2/7 = 14/21 + 6/21 = 20/21`       

`8xx3/5:12/5= 8xx 3/5 xx 5/12 = 24/5 xx 5/12 = 2`         

`4/9+3/4-1/3= (16/36 + 27/36 ) - 1/3 = 43/36 - 1/3 = 31/36`

`1/2xx3/4:6/5`

`=1/2xx3/4xx5/6`

`=3/8xx5/6`

`=15/48`

`=5/16`

__

`2/3+1/6:7/12`

`=2/3+1/6xx12/7`

`=2/3+2/7`

`=14/21+6/21`

`=20/21`

__

`8xx3/5:12/5`

`=8xx3/5xx5/12`

`=8xx1/4`

`=8/4`

`=2`

__

`4/9+3/4-1/3`

`=(4/9-1/3)+3/4`

`=(4/9-3/9)+3/4`

`=1/9+3/4`

`=4/36+27/36`

`=31/36`

a) Ta có x 6 + 2 x 3 + 3 x 3 − 1 . 3 x x + 1 . x 2 + x + 1 x 6 + 2 x 3 + 3 = 3 x x 2 − 1  

b) Gợi ý: a 3   +   2 a 2  - a - 2 = (a - 1)(a + 1) (a + 2)

Thực hiện phép tính từ trái qua phải thu được:  = 1 3

a: \(=2x^3-14x^2-6x\)

c: \(=-10x^5-15x^4+25x^3\)

a) 2x. (x2 – 7x -3)

= 2x³- 14x²- 6x

b) ( -2x3 + y2 -7xy). 4xy2 

= -8x⁴y²+ 4xy⁴- 28x²y³

c)(-5x3).(2x2+3x-5)

= -10x⁵-15x⁴+25x³

d) (2x2 - xy+ y2).(-3x3)

=-6x⁵+ 3x⁴y -3x³y²

e)(x2 -2x+3). (x-4) 

=x³-2x²+3x -4x²+8x-12

=x³-6x²+11x-12

f) ( 2x3 -3x -1). (5x+2)

=10x⁴-15x²-5x +4x³-6x-2

=10x⁴+4x³-15x²-11x-2

a ) 3/5 + 3/16 + 13/16 

= 3/5 + ( 3/16 + 13/16 ) 

= 3/5 + 16/16

= 3/5 + 1

= 3/5 + 5/5

= 8/5 

b ) 1/1 x 2 + 1/ 2 x 3 + 1/ 3 x 4

= 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4

= 1 - 1/4

= 4/4 - 1/4

= 3/4 

a) 3/5+3/16+13/16

=3/5+16/16

=3/5+1

=3/5+5/5

=8/5

a      =3/5+(3/16+13/16)=3/5+16/16=3/5+1=8/5

b        =1-1/2+1/2-1/3+1/3-1/4=1-1/4=3/4

(ở đầu câu mình để dấu bằng để trước dấu bằng bạn viết lại đề bài na)

Tách ra, dài quá mn đọc là mất hứng làm đó.