Bài 1:
a)25/x+1 - 7/6 = -1/3 -0,5
b)(4/3-1/4 . x -5/12) - 2x = 1,6 : 3/5
c)6/5 - 4/5 . (2/3x +1/9) = 150/7
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a: =>4/3x=7/9-4/9=1/3
=>x=1/4
b: =>5/2-x=9/14:(-4/7)=-9/8
=>x=5/2+9/8=29/8
c: =>3x+3/4=8/3
=>3x=23/12
hay x=23/36
d: =>-5/6-x=7/12-4/12=3/12=1/4
=>x=-5/6-1/4=-10/12-3/12=-13/12
Mình ko ghi lại đề , bạn ghi ra xong rồi suy ra như mình nha .
1) \(=>A=\left(6x^2+3x-10x-5\right)-\left(6x^2+14x-9x-21\right)\)
\(=>A=-12x+16\)
2) \(=>B=8x^3+27-8x^3+2=29\)
3)\(=>C=[\left(x-1\right)-\left(x+1\right)]^3=\left(-2\right)^3=-8\)
4)\(=>D=[\left(2x+5\right)-\left(2x\right)]^3=5^3=125\)
5)\(=>E=\left(3x+1\right)^2-\left(3x+5\right)^2+12x+2\left(6x+3\right)\)
\(=>E=\left(3x+1+3x+5\right)\left(3x+1-3x-5\right)+12x+12x+6\)
\(=>E=\left(6x+6\right)\left(-4\right)+24x+6=-24x-24+24x+6=-18\)
6)\(=>F=\left(2x^2+3x-10x-15\right)-\left(2x^2-6x\right)+x+7=-8\)
k cho mik nha ,
Ta có 1/2*3=1/2-1/3;
1/3*4=1/3-1/4
......................(tương tự với các số khác)
1/149*150=1/149-1/150
=>A=1/2-1/3+1/3-1/4+1/4-1/5+...-1/149+1/149-1/150=1/2-1/150
A=75/150-1/150=74/150=37/75
Vậy A= 37/75
a) \(\frac{25}{9}-\frac{12}{13}x=\frac{7}{9}\)
=> \(\frac{12}{13}x=\frac{25}{9}-\frac{7}{9}=\frac{18}{9}=2\)
=> \(x=2:\frac{12}{13}=2\cdot\frac{13}{12}=\frac{13}{6}\)
b) \(x:\frac{13}{3}=-2,5\)
=> \(x:\frac{13}{3}=-\frac{5}{2}\)
=> \(x=\left(-\frac{5}{2}\right)\cdot\frac{13}{3}=-\frac{65}{6}\)
c) \(\frac{x}{3}-\frac{1}{4}=-\frac{5}{6}\)
=> \(\frac{4x-3}{12}=-\frac{10}{12}\)
=> 4x - 3 = -10
=> 4x = -10 + 3 = -7
=> x = -7/4
Bài 2 :
\(A=a\cdot\frac{1}{3}+a\cdot\frac{1}{4}-a\cdot\frac{1}{6}=a\left(\frac{1}{3}+\frac{1}{4}-\frac{1}{6}\right)=a\cdot\frac{5}{12}\)
Thay a = -3/5 vào biểu thức ta có : \(A=\left(-\frac{3}{5}\right)\cdot\frac{5}{12}=\frac{-3}{12}=\frac{-1}{4}\)
\(B=b\cdot\frac{5}{6}+b\cdot\frac{3}{4}-b\cdot\frac{1}{2}=b\left(\frac{5}{6}+\frac{3}{4}-\frac{1}{2}\right)=b\cdot\frac{13}{12}\)
Thay b = 12/13 vào ta được kết quả là 1
a ) \(\frac{25}{9}-\frac{12}{13}\cdot x=\frac{7}{9}\)
\(\Rightarrow\frac{12}{13}\cdot x=\frac{25}{9}-\frac{7}{9}=\frac{18}{9}=2\)
\(\Rightarrow x=2\div\frac{12}{13}=2\cdot\frac{13}{12}=\frac{13}{6}\)
Vậy ...
b ) \(x\div\frac{13}{3}=-\frac{5}{2}\)
\(\Rightarrow x\div\frac{13}{3}=-\frac{5}{2}\)
\(\Rightarrow x=\left(-\frac{5}{2}\right)\cdot\frac{13}{3}=-\frac{65}{6}\)
Vậy ..
c ) \(\frac{x}{3}-\frac{1}{4}=-\frac{5}{6}\)
\(\Rightarrow\frac{4x-3}{12}=-\frac{10}{12}\)
\(\Rightarrow4x-3=-10\)
\(\Rightarrow4x=-10+3=-7\)
\(\Rightarrow x=-\frac{7}{4}\)
Vậy ....
Bài 2 :
a,\(\frac{x-1}{3}=2-\frac{x}{-2}\)
\(\Leftrightarrow\frac{x-1}{3}=\frac{-4-x}{-2}\Leftrightarrow-2x+2=-12-3x\Leftrightarrow x=-14\)
b, \(\frac{x-1}{x+5}=\frac{6}{7}\Leftrightarrow7x-7=6x+30\Leftrightarrow x=37\)
c, \(\frac{2x-1}{4}=\frac{4}{2x-1}\Leftrightarrow\left(2x-1\right)^2=16\)
\(\Leftrightarrow\left(2x-1\right)^2-4^2=0\Leftrightarrow\left(2x-5\right)\left(2x+3\right)=0\Leftrightarrow x=\frac{5}{2};-\frac{3}{2}\)
a) (x-2)3+6(x+1)2-x3+12=0
\(\Rightarrow\)x3-6x2+12x-8+6(x2+2x+1)-x3+12=0
\(\Rightarrow\)x3-6x2+12x-8+6x2+12x+6-x3+12=0
\(\Rightarrow\)24x+10=0
\(\Rightarrow\)24x=-10
\(\Rightarrow\)x=\(\dfrac{-10}{24}=\dfrac{-5}{12}\)
b)(x-5)(x+5)-(x+3)2+3(x-2)2=(x+1)2-(x-4)(x+4)+3x2
\(\Rightarrow\)x2-25-(x2+6x+9)+3(x2-4x+4)=x2+2x+1-(x2-16)+3x2
\(\Rightarrow\)x2-25-x2-6x-9+3x2-12x+12=x2+2x+1-x2+16+3x2
\(\Rightarrow\)3x2-18x-22=3x2+2x+17
\(\Rightarrow\)3x2-18x-22-3x2-2x-17=0
\(\Rightarrow\)-20x-39=0
\(\Rightarrow\)-20x=39
\(\Rightarrow\)x=\(-\dfrac{39}{20}\)
a)25/x+1 - 7/6 = 1/3 - 0,5
25/x+1 - 7/6 = 1/3 -1/2
25/x+1 - 7/6 = -1/6
25/x+1 = -1/6 + 7/6
25/x+1 = 1
25/x+1 = 25/25
=>25 = x + 1
x = 25 - 1
x = 24