Bài 1 :

a, ( 9/24 + - 18/24 + 14/24 ) . 6/5 + 1/2

= 5/24 . 6/5 + 1/2

= 1/4 + 1/2

= 3/4

b, -3/7 . ( 5/9 + 4/9 ) + 17/7

= - 3/7 . 1 + 17/7

= -3/7 + 17/7

= 14/7

Bài 2 :

a, ( 2/3 + 1/2 ) . x = 5/12

7/6 . x = 5/12

x = 5/12 : 7/6

x = 5/14

b, 14/5 . x - 50 = 51 . 2/3

14/5 . x - 50 = 34

14/5 . x = 34 + 50

14/5 . x = 84

x = 84 : 14/5

x = 30

a) \(22\frac{1}{2}\cdot\frac{7}{9}+50\%-1,25\)

\(=\frac{45}{2}\cdot\frac{7}{9}+\frac{50}{100}-\frac{125}{100}\)

\(=\frac{5}{2}\cdot\frac{7}{1}+\frac{1}{2}-\frac{5}{4}\)

\(=\frac{35}{2}+\frac{1}{2}-\frac{5}{4}=18-\frac{5}{4}=\frac{67}{4}\)

b) \(1,4\cdot\frac{15}{49}-\left(\frac{4}{5}+\frac{2}{3}\right):2\frac{1}{5}\)

\(=\frac{7}{5}\cdot\frac{15}{49}-\frac{22}{15}:\frac{11}{15}\)

\(=\frac{1}{1}\cdot\frac{3}{7}-\frac{22}{15}\cdot\frac{15}{11}\)

\(=\frac{3}{7}-2=\frac{3-14}{7}=\frac{-11}{7}\)

c) \(\left(-\frac{1}{2}\right)^2-\frac{7}{16}:\frac{7}{4}+75\%\)

\(=\frac{1}{4}-\frac{7}{16}\cdot\frac{4}{7}+\frac{75}{100}\)

\(=\frac{1}{4}-\frac{1}{4}+\frac{3}{4}=\frac{3}{4}\)

Bài 2  Bạn tự làm nhé

1.a,\(22\frac{1}{2}.\frac{7}{9}+50\%-1,25\)

\(=\frac{45}{2}.\frac{7}{9}+\frac{1}{2}-\frac{5}{4}\)

\(=\frac{35}{2}+\frac{1}{2}-\frac{5}{4}\)

\(=\frac{67}{4}\)

b,Các phép tính khác làm tương tự

Đổi các số ra hết thành phân số,có ngoặc thì lm ngoặc trc,Xoq đến nhân chia trước dồi mới cộng trừ

c,tương tự

2.

a,\(1\frac{3}{5}+\frac{7}{12}\div x=\frac{-9}{4}\)

\(\frac{8}{5}+\frac{7}{12}\div x=\frac{-9}{4}\)

\(\frac{7}{12}\div x=\frac{-77}{20}\)

Đến đây dễ bạn tự làm

b,\(\left(2\frac{4}{5}.x+50\right)\div\frac{2}{3}=-51\)

\(\left(\frac{14}{5}x+50\right)\div\frac{2}{3}=-51\)

\(\frac{14}{5}x+50=-34\)

\(\frac{14}{5}x=-84\)

Tự làm tiếp

c,\(\left|\frac{3}{4}.x-\frac{1}{2}\right|=\frac{1}{4}\)\(\Rightarrow\left|\frac{3}{4}x-\frac{1}{2}\right|=\varnothing\)

Những câu từ D trở đi là các câu riêng biệt ak bạn

\(A = {1\over2}-{3\over4}+{5\over6}-{7\over12}={6\over12}-{9\over12}+{10\over12}-{7\over12}\)\(={0\over12}=0\)

\(B=3-{2\over3}+{3\over5}(-{10\over9}-{25\over3})-{5\over6}\)\(={7\over3}+{3\over5}(-{10\over9}-{75\over9})-{5\over6}\)\(={14\over6}-{5\over6}+{3\over5}({-85\over9})\)\(={3\over2}-{17\over3}={9\over6}-{34\over6}={-25\over6}\)

a:=>x^2-1-x=2x-1

=>x^2-x-1=2x-1

=>x^2-3x=0

=>x=0(loại) hoặc x=3(nhận)

b:=>x+2=0 hoặc 5-3x=0

=>x=-2 hoặc x=5/3

c:=>20(1-2x)+6x=9(x-5)-24

=>20-40x+6x=9x-45-24

=>-34x+20=9x-69

=>-43x=-89

=>x=89/43

d: =>x^2+4x+4-x^2-2x+3=2x^2+8x-4x-16-3

=>2x^2+4x-19=-2x+7

=>2x^2+6x-26=0

=>x^2+3x-13=0

=>\(x=\dfrac{-3\pm\sqrt{61}}{2}\)

e: =>(2x-3)(2x-3-x-1)=0

=>(2x-3)(x-4)=0

=>x=4 hoặc x=3/2

\(\dfrac{x-1}{x}-\dfrac{1}{x+1}=\dfrac{2x-1}{x^2+x}\)

\(\Leftrightarrow\dfrac{x-1}{x}-\dfrac{1}{x+1}=\dfrac{2x-1}{x\left(x+1\right)}\)

ĐKXĐ : \(\left\{{}\begin{matrix}x\ne0\\x+1\ne0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\ne0\\x\ne-1\end{matrix}\right.\)

Ta có : `(x-1)/x -1/(x+1) =(2x-1)/(x(x+1))`

\(\Leftrightarrow\dfrac{\left(x-1\right)\left(x+1\right)}{x\left(x+1\right)}-\dfrac{x}{x\left(x+1\right)}=\dfrac{2x-1}{x\left(x+1\right)}\)

`=> x^2 +x -x-1 -x-2x+1=0`

`<=> x^2 -3x =0`

`<=> x(x-3)=0`

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x-3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\left(ktm\right)\\x=3\end{matrix}\right.\)

__

`(x+2)(5-3x)=0`

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

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

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

__

\(\dfrac{5\left(1-2x\right)}{3}+\dfrac{x}{2}=\dfrac{3\left(x-5\right)}{4}-2\)

\(\Leftrightarrow\dfrac{20\left(1-2x\right)}{12}+\dfrac{6x}{12}=\dfrac{9\left(x-5\right)}{12}-\dfrac{24}{12}\)

`<=> 2x- 40x + 6x = 9x - 45 -24`

`<=>  2x- 40x + 6x-9x + 45 +24=0`

`<=>-41x+69=0`

`<=>-41x=-69`

`<=> x=69/41`

Cậu tách 2 câu 1 lượt mn trl nhanh hơn đó ạ

a:=>x^2-1-x=2x-1

=>x^2-x-1=2x-1

=>x^2-3x=0

=>x=0(loại) hoặc x=3(nhận)

b:=>x+2=0 hoặc 5-3x=0

=>x=-2 hoặc x=5/3

c:=>20(1-2x)+6x=9(x-5)-24

=>20-40x+6x=9x-45-24

=>-34x+20=9x-69

=>-43x=-89

=>x=89/43

d: =>x^2+4x+4-x^2-2x+3=2x^2+8x-4x-16-3

=>2x^2+4x-19=-2x+7

=>2x^2+6x-26=0

=>x^2+3x-13=0

=>\(x=\dfrac{-3\pm\sqrt{61}}{2}\)

e: =>(2x-3)(2x-3-x-1)=0

=>(2x-3)(x-4)=0

=>x=4 hoặc x=3/2

\(a)\frac{2}{3}x-\frac{1}{2}=\frac{5}{12}\)

\(\Rightarrow\frac{2}{3}x=\frac{5}{12}+\frac{1}{2}=\frac{11}{12}\)

\(\Rightarrow x=\frac{11}{12}:\frac{2}{3}=\frac{11}{8}\)

\(b)\left(2\frac{4}{5}x-50\right):\frac{2}{3}=51\)

\(\Rightarrow\frac{14}{5}x-50=51.\frac{2}{3}=34\)

\(\Rightarrow\frac{14}{5}x=34+50=84\)

\(\Rightarrow x=84:\frac{14}{5}=30\)

a) 2/3.x - 1/2 = 5/12

            2/3.x = 5/12 + 1/2

            2/3.x = 11/12

                  x = 11/12 : 2/3

                   x = 11/8

b) \(\left(2\frac{4}{5}.x-50\right):\frac{2}{3}=51\)

                  \(\frac{14}{5}.x-50=51.\frac{2}{3}\)

                   \(\frac{14}{5}.x-50=34\)

                                \(\frac{14}{5}.x=34+50\)

                                \(\frac{14}{5}.x=84\)

                                         \(x=84:\frac{14}{5}\)

                                         \(x=30\)

Câu a \(\left|2x-\frac{1}{3}\right|+\frac{5}{6}=1\)

g) \(\left(x+\frac{1}{2}\right)\left(\frac{2}{3}-2x\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x+\frac{1}{2}=0\\\frac{2}{3}-2x=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{-1}{2}\\x=\frac{1}{3}\end{cases}}\)

Vây \(x\in\left\{\frac{-1}{2};\frac{1}{3}\right\}\)

i) \(\frac{6}{2}=\frac{-5+x}{15}\)

\(\Leftrightarrow3=\frac{x-5}{15}\)

\(\Leftrightarrow x-5=15.3\)

\(\Leftrightarrow x-5=45\)

\(\Leftrightarrow x=45+5\)

\(\Leftrightarrow x=50\)

d: =>4x+6=15x-12

=>4x-15x=-12-6=-18

=>-11x=-18

hay x=18/11

e: =>\(45x+27=12+24x\)

=>21x=-15

hay x=-5/7

f: =>35x-5=96-6x

=>41x=101

hay x=101/41

g: =>3(x-3)=90-5(1-2x)

=>3x-9=90-5+10x

=>3x-9=10x+85

=>-7x=94

hay x=-94/7