a,x=7                b, x=.....

Yêu cầu về bài toán này là gì?

cần đề bài

Viết số thập phân dưới dạng phân số

a) x⁴+x³+2x²+x+1=(x⁴+x³+x²)+(x²+x+1)=x²(x²+x+1)+(x²+x+1)=(x²+x+1)(x²+1)

b)a³+b³+c³-3abc=a³+3ab(a+b)+b³+c³ -(3ab(a+b)+3abc)=(a+b)³+c³-3ab(a+b+c)

=(a+b+c)((a+b)²-(a+b)c+c²)-3ab(a+b+c)=(a+b+c)(a²+2ab+b²-ac-ab+c²-3ab)=(a+b+c)(a²+b²+c²-ab-ac-bc)

c)Đặt x-y=a;y-z=b;z-x=c

a+b+c=x-y-z+z-x=o

đưa về như bài b

d)nhóm 2 hạng tử đầu lại và 2hangj tử sau lại để 2 hạng tử sau ở trong ngoặc sau đó áp dụng hằng đẳng thức dề tính sau đó dặt nhân tử chung

e)x²(y-z)+y²(z-x)+z²(x-y)=x²(y-z)-y²((y-z)+(x-y))+z²(x-y)

=x²(y-z)-y²(y-z)-y²(x-y)+z²(x-y)=(y-z)(x²-y²)-(x-y)(y²-z²)=(y-z)(x²-2y²+xy+xz+yz)

\(\frac{1}{2}x+\frac{1}{5}x+\frac{3}{5}=0\)

=> \(\left(\frac{1}{2}+\frac{1}{5}\right)x+\frac{3}{5}=0\)

=> \(\frac{7}{10}x+\frac{3}{5}=0\)

=> \(\frac{7}{10}x=-\frac{3}{5}\)

=> \(x=\left(-\frac{3}{5}\right):\frac{7}{10}=\left(-\frac{3}{5}\right)\cdot\frac{10}{7}=\left(-\frac{3}{1}\right)\cdot\frac{2}{7}=-\frac{6}{7}\)

b) \(\left|2\frac{1}{2}+x\right|-\left(-\frac{2}{3}\right)=3\)

=> \(\left|\frac{5}{2}+x\right|+\frac{2}{3}=3\)

=> \(\left|\frac{5}{2}+x\right|=\frac{7}{3}\)

=> \(\orbr{\begin{cases}\frac{5}{2}+x=\frac{7}{3}\\\frac{5}{2}+x=-\frac{7}{3}\end{cases}}\Rightarrow\orbr{\begin{cases}x=-\frac{1}{6}\\x=-\frac{29}{6}\end{cases}}\)

c) \(\left|x+\frac{4}{15}\right|-\left|-3.75\right|=-\left|-2,15\right|\)

=> \(\left|x+\frac{4}{15}\right|-3,75=-2,15\)

=> \(\left|x+\frac{4}{15}\right|=\frac{8}{5}\)

=> \(\orbr{\begin{cases}x+\frac{4}{15}=\frac{8}{5}\\x+\frac{4}{15}=-\frac{8}{5}\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{4}{3}\\x=-\frac{28}{15}\end{cases}}\)

a, \(\frac{1}{2}x+\frac{1}{5}x+\frac{3}{5}=0\Leftrightarrow\frac{7}{10}x+\frac{3}{5}=0\Leftrightarrow x=-\frac{6}{7}\)

b, đề sai 

c, \(\left|\frac{x+4}{15}\right|-\left|-3,75\right|=-\left|-2,15\right|\)

\(\Leftrightarrow\frac{x+4}{15}-3,75=-2,15\Leftrightarrow\frac{x+4}{15}=\frac{8}{5}\Leftrightarrow x+4=24\Leftrightarrow x=28\)

đây bạn

tìm x biết:

(3x-1) [- 1/2x+5]=0

1/4+1/3:(2x-1)=-5

[2x+3/5]² - 9/25=0

-5(x+1/5)-1/2(x-2/3)=3/2x - 5 /6

[x+1/2]x [2/3-2x]=0

17/2-|2x-3/4|=-7/4

2/3x-1/2x =5/12

(x+1/5)²+17/25=26/25

[x.44/7+3/7].11/5-3/7=-2

3[3x-1/2]+1/9=0

Toán lớp 6Tìm x

 Trả lời  Câu hỏi tương tự

Chưa có ai trả lời câu hỏi này,bạn hãy là người đâu tiên giúp nguyenvanhoang giải bài toán này !

3(3x-1/2)^3+1/9=0

\(1,\)

\(a,\dfrac{11}{125}-\dfrac{17}{18}-\dfrac{5}{7}+\dfrac{4}{9}+\dfrac{17}{14}\)

\(=\dfrac{11}{125}+\left(\dfrac{4}{9}-\dfrac{17}{18}\right)+\left(\dfrac{17}{14}-\dfrac{5}{7}\right)\)

\(=\dfrac{11}{125}+\left(\dfrac{-1}{2}\right)+\dfrac{1}{2}\)

\(=\dfrac{11}{125}\)

\(b,-1\dfrac{5}{7}.15+\dfrac{2}{7}.\left(-15\right)+\left(-105\right).\left(\dfrac{2}{3}-\dfrac{4}{5}+\dfrac{1}{7}\right)\)

\(=\dfrac{-12}{7}.15+\dfrac{2}{7}.\left(-15\right)+\left(105\right).\left(\dfrac{2}{3}-\dfrac{4}{5}+\dfrac{1}{7}\right)\)

\(=-15.\left[\dfrac{12}{7}+\dfrac{2}{7}+\left(-5\right).\left(\dfrac{2}{3}-\dfrac{4}{5}+\dfrac{1}{7}\right)\right]\)

\(=-15.\left[2+\left(-5\right).\dfrac{1}{105}\right]\)

\(=-15.\left(2-\dfrac{1}{21}\right)\)

\(=-15.\dfrac{41}{21}=\dfrac{-615}{21}\)

\(2,\)

\(a,\dfrac{11}{13}-\left(\dfrac{5}{42}-x\right)=-\left(\dfrac{15}{28}-\dfrac{11}{13}\right)\)

\(\Leftrightarrow\dfrac{11}{13}-\dfrac{5}{42}+x=\dfrac{-15}{28}+\dfrac{11}{13}\)

\(\Leftrightarrow x=\dfrac{-15}{28}+\dfrac{11}{13}-\dfrac{11}{13}+\dfrac{5}{42}\)

\(\Leftrightarrow x=\left(\dfrac{11}{13}-\dfrac{11}{13}\right)+\left(\dfrac{5}{42}+\dfrac{-15}{28}\right)\)

\(\Leftrightarrow x=\dfrac{5}{12}\)

Vậy \(x=\dfrac{5}{12}\)

\(b,\left|x+\dfrac{4}{15}\right|-\left|-3,75\right|=-\left|-2,15\right|\)

\(\Leftrightarrow\left|x+\dfrac{4}{15}\right|-3,75=-2,15\)

\(\Leftrightarrow\left|x+\dfrac{4}{15}\right|=-2,15+3,75=1,6=\dfrac{16}{10}=\dfrac{8}{5}\)

\(\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{4}{15}=\dfrac{8}{5}\\x+\dfrac{4}{15}=\dfrac{-8}{5}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{8}{5}-\dfrac{4}{15}=\dfrac{4}{3}\\x=\dfrac{-8}{5}-\dfrac{4}{15}=\dfrac{-28}{15}\end{matrix}\right.\)

Vậy \(x\in\left\{\dfrac{4}{3};\dfrac{-28}{15}\right\}\)

\(c,7^{x+2}+2.7^{x-1}=345\)

\(\Leftrightarrow7^{x-1}.\left(7^3+2\right)=345\)

\(\Leftrightarrow7^{x-1}.\left(343+2\right)=345\)

\(\Leftrightarrow7^{x-1}.345=345\)

\(\Leftrightarrow7^{x-1}=345:345=1\)

\(\Leftrightarrow x-1=0\)

\(x=0+1=1\)

Vậy \(x=1\)

a,   11/13 - ( 5/42 - x ) = - (5/28 - 11/13)

    11/13 - (5/42 - x) = - 5/28 + 11/13

    - (5/42 - x) + 5/28 = -11/13 + 11/13

 - 5/42 + x + 5/28 = 0

- 5/42 + x = 0 - 5/28

- 5/42 + x = - 5/28

x = -5/28 +5/42

x = - 5/84

b, / x + 4/15 \ - / - 3,75 \ = - / - 2,15 \

./ x + 4/15 \ - 3,75 = - 2,15

/ x + 4/15 \ = -2,15 + 3,75

/ x + 4/15 \ = 1,6

x + 4 / 15 = 1,6                      hoặc x+ 4/15 = - 1,6

x = 1,6 - 4/15                                   x = - 1,6 -4/15

x = 4/3                                              x = -28/15

Vậy x = 4/3 hoặc x = - 28/15

c, ( 0,25 - 30% x ) . 1/3 = 1/4 - 31/6

( 1/4 - 3/10 x ) . 1/3 = - 59/12

( 1/4 - 3/10 x ) = - 59/12 : 1/3

1/4 - 3/10 x = - 59/4

3/10 x = 1/4 + 59/4

3/10 x = 15

x = 15 : 3/10

x = 50

d, ( x - 1/2 ) : 1/3 + 5/7 = 68/7

( x - 1/2 ) : 1/3 = 68/7 - 5/7

( x - 1/2 ) : 1/3 = 63/7

( x - 1/2 ) = 63/7 . 1/3

x -1/2 = 3 

x = 3 + 1/2

x = 7/2