a: \(\Leftrightarrow x\cdot\dfrac{3}{5}=\dfrac{-1}{7}+\dfrac{1}{2}=\dfrac{1}{2}-\dfrac{1}{7}=\dfrac{5}{14}\)

\(\Leftrightarrow x=\dfrac{5}{14}:\dfrac{3}{5}=\dfrac{25}{42}\)

b: =>|3x-1|=2

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

c: \(\Leftrightarrow7\left(37-x\right)=3\left(x-13\right)\)

=>259-7x=3x-39

=>-10x=-298

hay x=29,8

d: =>x=3/4+2/3=9/12+8/12=17/12

câu trả lời đây 

(3x/5 - 3/4):3/7 =14/5

(3x/5-3/4).7/3 =21x/15 - 21/12 = 14/5

21x =( 14/5 +21/12).15

21x = 273/4

x = 13/4

đã làm là đúng 

x = 

a, \(\Leftrightarrow2x^2=72\)

\(\Leftrightarrow x^2=36\)

\(\Leftrightarrow x=\pm6\)

Vậy ...

\(b,\Leftrightarrow\dfrac{3}{5}x-0,75=2\dfrac{4}{5}.\dfrac{3}{7}=\dfrac{6}{5}\)

\(\Leftrightarrow\dfrac{3}{5}x=\dfrac{6}{5}+0,75=\dfrac{39}{20}\)

\(\Leftrightarrow x=\dfrac{39}{20}:\dfrac{3}{5}=\dfrac{13}{4}\)

Vậy ...

\(c,\Leftrightarrow2x=1\dfrac{5}{6}.\dfrac{6}{11}-\dfrac{3}{10}=\dfrac{7}{10}\)

\(\Leftrightarrow x=\dfrac{7}{10}:2=\dfrac{7}{20}\)

Vậy ...

\(d,\Leftrightarrow\dfrac{1}{x-7\dfrac{1}{3}}=1.5:2\dfrac{1}{4}=\dfrac{2}{3}\)

\(\Leftrightarrow x-7\dfrac{1}{3}=\dfrac{3}{2}\)

\(\Leftrightarrow x=\dfrac{3}{2}+7\dfrac{1}{3}=\dfrac{53}{6}\)

Vậy ...

a) 2x² - 72 = 0

\(\Rightarrow\) 2x² = 72

\(\Rightarrow\) x² = 36 = 6² = (- 6)²

\(\Rightarrow\) x = 6 hoặc x = - 6

Vậy x = 6 hoặc x = - 6

b) (\(\dfrac{3}{5}\)x - 0,75) : \(\dfrac{3}{7}\) = \(2\dfrac{4}{5}\)

\(\Rightarrow\)  (\(\dfrac{3}{5}\)x - 0,75) : \(\dfrac{3}{7}\) = \(\dfrac{14}{5}\)

\(\Rightarrow\)  \(\dfrac{3}{5}\)x - \(\dfrac{3}{4}\) = \(\dfrac{6}{5}\)

\(\Rightarrow\) \(\dfrac{3}{5}\)x = \(\dfrac{39}{20}\)

\(\Rightarrow\) x = \(\dfrac{13}{4}\)

Vậy x = \(\dfrac{13}{4}\)

c) \(2x+\dfrac{3}{10}=1\dfrac{5}{6}.\dfrac{6}{11}\)

\(\Rightarrow\) \(2x+\dfrac{3}{10}=\dfrac{11}{6}.\dfrac{6}{11}=1\)

\(\Rightarrow\) \(2x=\dfrac{7}{10}\)

\(\Rightarrow\) \(x=\dfrac{7}{20}\)

Vậy \(x=\dfrac{7}{20}\)

d) \(2\dfrac{1}{4}:\left(x-7\dfrac{1}{3}\right)=1,5\)

\(\Rightarrow\) \(\dfrac{9}{4}:\left(x-\dfrac{22}{3}\right)=\dfrac{3}{2}\)

\(\Rightarrow\) \(x-\dfrac{22}{3}=\dfrac{3}{2}\)

\(\Rightarrow\) \(x=\dfrac{53}{6}\)

Vậy \(x=\dfrac{53}{6}\)

a) A = x²( x + y ) - y( x² + y² )

= x³ + x²y - x²y - y³

= x³ - y³

Với x = 1 ; y = -1

A = 1³ - (-1)³ = 1 + 1 = 2

b) B = 5x( x - 4y ) - 4y( y - 5x )

= 5x² - 20xy - 4y² + 20xy

= 5x² - 4y²

Với x = -0, 6 ; y = -0, 75

B = 5.(-0, 6)² - 4.(-0, 75)² = 5.9/25 - 4.9/16 = 9/5 - 9/4 = -9/20

C = x( x - y + 1 ) - y( y + 1 - x )

= x² - xy + x - y² - y + xy

= x² + x - y² - y

= ( x² - y² ) + ( x - y )

= ( x - y )( x + y ) + ( x - y )

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

Thế x = -2/3 ; y = -1/3 ta được 

C = [ -2/3 - (-1/3 ) ][ -2/3 - 1/3 + 1 ]

    = ( -2/3 + 1/3 ).0

    = 0

a, \(A=x^2\left(x+y\right)-y\left(x^2+y^2\right)+2002=x^3-y^3+2002\)

Thay x = 1; y = -1 ta có : \(1^3-\left(-1\right)^3+2002=1-1+2002=2002\)

b, \(5x\left(x-4y\right)-4y\left(y-5x\right)-\frac{11}{20}=5x^2-4y^2-\frac{11}{20}\)

Thay x = -0,6 ; y = -0,75 ta có : \(5.\left(-0,6\right)^2-4\left(-0,75\right)^2-\frac{11}{20}=-1\)

c, \(x\left(x-y+1\right)-y\left(y+1-x\right)=x^2+x-y^2-y\)

Thay x = -2/3 ; y = -1/3 ta có : \(\left(-\frac{2}{3}\right)^2-\frac{2}{3}-\left(-\frac{1}{3}\right)^2+\frac{1}{3}=0\)

a) \(A=x^2\left(x+y\right)-y\left(x^2+y^2+2002\right)\)với \(x=1;y=-1\)

\(A=x^3-y^3-2002y\)

Thay: x=1;y=-1, ta có:

\(1^3-\left(-1\right)^3-2002\left(-1\right)\Rightarrow1+1+2002=2004\)

b) \(B=4x\left(x-4y\right)-4y\left(y-5x\right)-\frac{11}{20}\)với \(x=-0,6;y=-0,75\)

\(B=4x^2-4y^2+4xy-\frac{11}{20}\)

\(B=4\left(x^2-y^2+xy\right)-\frac{11}{20}\)

Thay: x= -0,6; y=-0.75, ta có:

\(4\left(-0.6^2--0.75^2+\left(-0,6.-0,75\right)\right)\Rightarrow4\left(0.35.8875\right)=0,143.55\)

c) \(C=x\left(x-y+1\right)-y\left(y+1-x\right)\)với x=-2/3; y=-1/3

\(C=x^2+x-y^2-y\)

Thay: x=-2/3; y=-1/3, ta có:

\(C=\left(-\frac{2}{3}\right)^2-\frac{2}{3}-\left(-\frac{1}{3}\right)^2+\frac{1}{3}=\frac{4}{9}-\frac{6}{9}-\frac{1}{9}=-\frac{3}{9}=-\frac{1}{3}\)

\(\text{a) 5(2x-3)-4(5x-7)=19-2(x+11)}\)

\(10x-15-20x+28=19-2x-22\)

\(10x-20x+2x=19-22-28+15\)

\(-8x=-16\)

\(\Rightarrow x=2\)

\(\text{b) 4(x+3)-7x+17=8(5x-1)+166}\)

\(4x+12-7x+17=40x-8+166\)

\(4x-7x-40x=-8+166-17-12\)

\(-43x=129\)

\(x=-3\)

\(\text{c) 17-14(x+1)=13-4(x+1)-5(x-3)}\)

\(17-14x+14=13-4x-4-5x+15\)

\(-14x+4x+5x=13-4+15-14-17\)

\(-5x=-7\)

\(x=\frac{7}{5}\)

\(\text{d) 5x+3,5+(3x-4)=7x-3(x-0,5)}\)

\(5x+3,5+3x-4=7x-3x+1,5\)

\(5x+3x-7x+3x=1,5-3,5\)

\(x=-2\)

\(\text{e) 7(4x+3)-4(x-1)=15(x+0,75)+7}\)

\(28x+21-4x+4=15x+11,25+7\)

\(28x-4x-15x=11,25+7-4-21\)

\(9x=\frac{-27}{4}\)

\(x=\frac{-3}{4}\)

\(\text{f) 3x+2,42+o,8x=3,38-0,2x}\)

\(3x+0,8x+0,2x=3,38-2,42\)

\(4x=\frac{24}{25}\)

\(x=\frac{6}{25}\)

chúc bạn học tốt !!

minh moi hoc lop 5 thoi

1) 3x - 6=  5x + 2

5x - 3x = -6 - 2

2x = -8

x = -4

2) 15 - x = 4x - 5

4x + x = 15 + 5

5x = 20

x = 4

Tương tự như trên 

1) 3x - 6 = 5x + 2

  3x - 5x = 2 + 6

        -2x = 8

           x = 8 : (-2)

           x = -4

2) 15 - x = 4x - 5

    -x - 4x = -5 - 15

         -5x = -20

            x = -20 : (-5)

            x = 4