+) \(\dfrac{1}{3}x=-\dfrac{4}{3}-\dfrac{1}{2}=-\dfrac{11}{6}\)

\(x=-\dfrac{11}{6}:\dfrac{1}{3}=-\dfrac{11}{2}\)

+) \(\dfrac{4}{3}x=-\dfrac{2}{3}+\dfrac{1}{2}=-\dfrac{1}{6}\)

\(x=-\dfrac{1}{6}:\dfrac{4}{3}=-\dfrac{1}{8}\)

+) \(2\left(x-1\right)=\dfrac{5}{2}+\dfrac{2}{3}=\dfrac{19}{6}\)

\(x-1=\dfrac{19}{12}\)

\(x=\dfrac{31}{12}\)

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

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

\(\dfrac{1}{3}x=-\dfrac{11}{6}\)

\(x=\left(-\dfrac{11}{6}\right):\dfrac{1}{3}\)

\(x=-\dfrac{11}{2}\)

\(-\dfrac{2}{3}-\dfrac{4}{3}x=-\dfrac{1}{2}\)

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

\(\dfrac{4}{3}x=-\dfrac{1}{6}\)

\(x=\left(-\dfrac{1}{6}\right):\dfrac{4}{3}\)

\(x=-\dfrac{1}{8}\)

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

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

\(2\left(x-1\right)=\dfrac{19}{6}\)

\(\left(x-1\right)=\dfrac{19}{6}:2\)

\(x-1=\dfrac{19}{12}\)

\(x=\dfrac{19}{12}+1\)

\(x=\dfrac{31}{12}\)

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

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

\(\dfrac{-7}{2}x=\left(-\dfrac{1}{2}\right)+\dfrac{1}{3}\)

\(\dfrac{-7}{2}x=-\dfrac{1}{6}\)

\(x=\left(-\dfrac{1}{6}\right):\left(-\dfrac{7}{2}\right)\)

\(x=\dfrac{1}{21}\)

\(\dfrac{8}{5}-\dfrac{1}{2}:x=\dfrac{8}{3}\)

\(\dfrac{1}{2}:x=\dfrac{8}{5}-\dfrac{8}{3}\)

\(\dfrac{1}{2}:x=-\dfrac{16}{15}\)

\(x=\dfrac{1}{2}:\left(-\dfrac{16}{15}\right)\)

\(x=-\dfrac{15}{32}\)

\(-\dfrac{5}{4}x-\dfrac{1}{2}x=-\dfrac{7}{3}\)

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

\(x\cdot\left(-\dfrac{7}{4}\right)=-\dfrac{7}{3}\)

\(x=\left(-\dfrac{7}{3}\right):\left(-\dfrac{7}{4}\right)\)

\(x=\dfrac{4}{3}\)

a: =>(x-2)^3*[(x-2)^2-1]=0

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

=>\(x\in\left\{1;2;3\right\}\)

b: =>(x-3)^2*(x-3-1)=0

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

=>x=3 hoặc x=4

c: =>\(11\cdot\dfrac{6^x}{6}+2\cdot6^x\cdot6=6^{11}\left(11+2\cdot6^2\right)\)

=>6^x(11/6+12)=6^12(11/6+12)

=>x=12

\(4,7\div0,25+5,3\times4\)

\(=18,8+21,2\)

\(=40\)

\(3\times\left(a-2\right)+150=240\)

\(3\times\left(a-2\right)=90\)

\(a-2=30\)

\(a=32\)

\(\dfrac{1}{9}+a+\dfrac{7}{12}=\dfrac{17}{18}\)

\(\dfrac{1}{9}+a=\dfrac{13}{36}\)

\(a=\dfrac{1}{4}\)

\(\left(\dfrac{1}{2}\times\dfrac{1}{3}+\dfrac{1}{3}\times\dfrac{1}{4}+\dfrac{1}{4}\times\dfrac{1}{5}+\dfrac{1}{5}\times\dfrac{1}{6}+\dfrac{1}{6}\times\dfrac{1}{7}+\dfrac{1}{7}\times\dfrac{1}{8}\right)\times a=\dfrac{9}{16}\)

\(\left(\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}+\dfrac{1}{7\times8}\right)\times a=\dfrac{9}{16}\)

\(\left(\dfrac{1}{2}-\dfrac{1}{8}\right)\times a=\dfrac{9}{16}\)

\(\dfrac{3}{8}\times a=\dfrac{9}{16}\)

\(a=\dfrac{3}{2}\)

Bài 1

2/5 - 3/5 : (0,75 + 30%)

= 2/5 - 3/5 : 21/20

= 2/5 - 4/7

= -6/35

‐--------------------

Bài 2

a) x/6 = -11/3

x = -11/3 . 6

x = -22

b) 16/5 của x là 48

x = 48 : 16/5

x = 15

bài1

2/5-3/5:(0,75+30%)=2/5-3/5:(75/100+30/100)

                               =2/5-3/5:105/100

                               =2/5-3/5:21/20

                               = 2/5-3/5. 20/21

                               =2/5-1/1.4/7

                               =2/5-4/7

                               =2/5+-4/7

                               =14/35+-20/35

                               =34/35

2: 

a: =>x-1/5=2/15

=>x=2/15+3/15=5/15=1/3

b: =>x+7/12=-5/6-2/6=-7/6

=>x=-14/12-7/12=-21/12=-7/4

c: =>x+2/3=-10/3

=>x=-4

d: =>1/4:x=-11/4

=>x=-1/4:11/4=-1/11

e: =>8:x=1,6

=>x=5

\(a)P\left(x\right)=5x^5+3x-4x^4-2x^3+6+4x^2\)

   \(P\left(x\right)=5x^5-4x^4-2x^3+4x^2+3x+6\)

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

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

\(a)P\left(x\right)-Q\left(x\right)=\left(5x^5-4x^4-2x^3+4x^2+3x+6\right)+\left(-x^5+2x^4-2x^3+3x^2-x+\dfrac{1}{4}\right)\)

\(P\left(x\right)-Q\left(x\right)=5x^5-4x^4-2x^3+4x^2+3x+6+x^5-2x^4+2x^3-3x^2+x-\dfrac{1}{4}\)

\(P\left(x\right)-Q\left(x\right)=\left(5x^5+x^5\right)+\left(-4x^4-2x^4\right)+\left(-2x^3+2x^3\right)+\left(4x^2-3x^2\right)+\left(3x+x\right)+\left(6-\dfrac{1}{4}\right)\)

\(P\left(x\right)-Q\left(x\right)=6x^5-6x^4+x^2+4x+\dfrac{23}{4}\)

\(\text{c)Thay x=-1 vào biểu thức P(x),ta được:}\)

\(P\left(x\right)=5.\left(-1\right)^5-4.\left(-1\right)^4-2.\left(-1\right)^3+4.\left(-1\right)^2+3.\left(-1\right)+6\)

\(P\left(x\right)=\left(-5\right)-4-\left(-2\right)+4+\left(-3\right)+6\)

\(P\left(x\right)=\left(-9\right)-\left(-2\right)+4+\left(-3\right)+6\)

\(P\left(x\right)=\left(-7\right)+4+\left(-3\right)+6\)

\(P\left(x\right)=\left(-3\right)+\left(-3\right)+6\)

\(P\left(x\right)=\left(-6\right)+6=0\)

\(\text{Vậy giá trị của P(x) tại x=-1 là:0}\)

\(\text{Vậy =-1 là nghiệm của P(x)}\)

\(\text{Thay x=-1 vào biểu thức Q(x),ta được:}\)

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

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

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

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

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

\(Q\left(x\right)=\left(-3\right)+\dfrac{1}{4}=\dfrac{-13}{4}\)

\(\text{Vậy x=-1 không phải là nghiệm của Q(x)}\)

\(\text{d)Thay x=-1 vào biểu thức }P\left(x\right)-Q\left(x\right),\text{ta được:}\)

\(P\left(x\right)-Q\left(x\right)=6.\left(-1\right)^5-6.\left(-1\right)^4+\left(-1\right)^2+4.\left(-1\right)+\dfrac{23}{4}\)

\(P\left(x\right)-Q\left(x\right)=\left(-6\right)-6+1+\left(-4\right)+\dfrac{23}{4}\)

\(P\left(x\right)-Q\left(x\right)=\left(-12\right)+1+\left(-4\right)+\dfrac{23}{4}\)

\(P\left(x\right)-Q\left(x\right)=\left(-11\right)+\left(-4\right)+\dfrac{23}{4}\)

\(P\left(x\right)-Q\left(x\right)=\left(-15\right)+\dfrac{23}{4}=\dfrac{-37}{4}\)

\(\text{Vậy giá trị của P(x)-Q(x) tại x=-1 là:}\dfrac{-37}{4}\)

a: =>x/27+1=-2/3

=>x/27=-5/3

=>x=-45

b: \(\Leftrightarrow x-4=\dfrac{2}{5}:\dfrac{20}{21}=\dfrac{2}{5}\cdot\dfrac{21}{20}=\dfrac{42}{100}=\dfrac{21}{50}\)

=>x=221/50

c: \(\Leftrightarrow x+\dfrac{2}{3}=\dfrac{4}{60}=\dfrac{1}{15}\)

=>x=1/15-2/3=1/15-10/15=-9/15=-3/5

d: \(\Leftrightarrow x\cdot\dfrac{3}{5}=\dfrac{1}{5}-\dfrac{15}{14}\cdot\dfrac{21}{20}\)

=>\(x\cdot\dfrac{3}{5}=\dfrac{1}{5}-\dfrac{3}{2}\cdot\dfrac{3}{4}=\dfrac{1}{5}-\dfrac{9}{8}=\dfrac{-37}{40}\)

=>x=-37/24

e: =>-3/7x=84/45

=>x=-196/45

f: =>11/10x=-2/3

=>x=-20/33

toán 5 mà khó thế bn

\(A=\dfrac{1}{2}\times\left(\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+...+\dfrac{1}{2011}-\dfrac{1}{2013}\right)=\dfrac{1}{2}\times\left(\dfrac{1}{5}-\dfrac{1}{2013}\right)=\dfrac{1004}{10065}\)

a) \(\dfrac{4}{5}\left(x-\dfrac{1}{3}\right)-3\dfrac{1}{2}=50\%\)

\(\dfrac{4}{5}x-\dfrac{4}{15}-\dfrac{7}{2}=\dfrac{1}{2}\)

\(\dfrac{4}{5}x=\dfrac{1}{2}+\dfrac{7}{2}+\dfrac{4}{15}\)

\(\dfrac{4}{5}x=\dfrac{64}{15}\)

\(x=\dfrac{64}{15}:\dfrac{4}{5}\\ x=\dfrac{16}{3}\)

b) \(8\dfrac{3}{5}.x-2\dfrac{1}{5}.x=16\%\)

\(\dfrac{43}{5}x-\dfrac{11}{5}x=\dfrac{4}{25}\)

\(\dfrac{32}{5}x=\dfrac{4}{25}\)

\(x=\dfrac{4}{25}:\dfrac{32}{5}\)

\(x=\dfrac{1}{40}\)