dap an bang 170

dap an bang 170

(17 x 12 + 17 x 20 - 17 x 22 ) x ( \(\frac{3}{2}-\frac{4}{6}+\frac{1}{6}\) )

= 17 x ( 12 + 20 - 22 ) x ( \(\frac{9}{6}-\frac{4}{6}+\frac{1}{6}\))

= 17 x 10 x 1

= 170

\(7-\left(11+x-13\right)\div2\frac{2}{3}=2\)

\(\left(11+x-13\right)\div2\frac{2}{3}=7-2\)

\(\left(11+x-13\right)\div2\frac{2}{3}=5\)

\(11+x-13=\frac{40}{3}\)

\(11+x=\frac{79}{3}\)

\(x=\frac{46}{3}\)

Ta có:

\(7-\left(11+x-13\right)\div2\frac{2}{3}=2\)

\(7-\left(11+x-13\right)=2.2\frac{2}{3}\)

\(7-\left(11+x-13\right)=\frac{16}{3}\)

\(11+x-13=7-\frac{16}{3}\)

\(11+x-13=\frac{5}{3}\)

\(11+x=\frac{5}{3}+13\)

\(11+x=\frac{44}{3}\)

\(x=\frac{44}{3}-11\)

\(x=\frac{11}{3}\)

43/3 mình ko chắc nhé :)

Tờ làm luôn, ko ghi đề nữa nhé

\(A=\frac{\frac{24}{12}-\frac{4}{12}+\frac{3}{12}}{\frac{24}{12}+\frac{2}{12}-\frac{3}{12}}\)

\(A=\frac{\frac{23}{12}}{\frac{23}{12}}=1\)

Vậy A=1

\(A=\frac{2-\frac{1}{3}+\frac{1}{4}}{2+\frac{1}{6}-\frac{1}{4}}\)\(=\frac{2-\frac{2}{6}+\frac{2}{8}}{2+\frac{2}{12}-\frac{2}{8}}\)\(=\frac{2\left(1-\frac{1}{6}+\frac{1}{8}\right)}{-2\left(1-\frac{1}{12}+\frac{1}{8}\right)}\)\(=-1\)

31/12

51/24 

nha

7 -  ( 11 + x -13 ) :  \(2\frac{2}{3}\)  = 2

(11+ x - 13) : \(2\frac{2}{3}\) = 7-2

(11 + x - 13) : \(2\frac{2}{3}\)= 5

11 + x - 13 = 5 . \(2\frac{2}{3}\)

11 + x - 13 = \(\frac{40}{3}\)

11 + x = \(\frac{40}{3}+13\)

11 + x = \(\frac{79}{3}\)

x = \(\frac{79}{3}-11\)

x = \(\frac{46}{3}\)

\(7-\left(11+x-13\right):2\frac{2}{3}=2\)

\(7-\left(11+x-13\right)=2.2\frac{2}{3}\)

\(7-\left(11+x-13\right)=\frac{16}{3}\)

\(11+x-13=7-\frac{16}{3}\)

\(11+x-13=\frac{5}{3}\)

\(11+x=\frac{5}{3}+13\)

\(11+x=\frac{44}{3}\)

\(x=\frac{44}{3}-11\)

\(x=\frac{11}{3}\)

=>7-(11+x-13):8/3=2

=>    (11+x-13):8/3=7-2

=>     (11+x-13):8/3=5

=>    (11+x-13)      =5x8/3

=>    11+x-13        =40/3

=>     11+x            =40/3+13

=>      11+x           =79/3

=>             x=79/3-11

=>              x=46/3

ai tk mk nhiều nhất và nhanh nhất mk sẽ tk cho 

48

6

7 tk nha

2 x 2 x 3 x 4 = 48

1 x 2 x 3 = 6

1 + 6 = 7

\(\left(x+y+z\right)\left(\frac{1}{x}+\frac{1}{y}+\frac{1}{z}\right)\ge9\) nha bạn!

ko hỉu thì ib

\(\left(x+y+z\right).\left(\frac{1}{z}+\frac{1}{y}+\frac{1}{x}\right)\ge9\) với x,y,z dương hay jj đó chứ? (cái này t k bt -.-) VD: x=2, y=-2,z=4

=> \(\left(x+y+z\right).\left(\frac{1}{z}+\frac{1}{y}+\frac{1}{x}\right)=\left(2-2+4\right).\left(\frac{1}{2}-\frac{1}{2}+\frac{1}{4}\right)=1\)

-----------------------------------------------------------------------------------------

\(\left(x+y+z\right).\left(\frac{1}{x}+\frac{1}{y}+\frac{1}{z}\right)=1\)

\(\Leftrightarrow\left(x+y+z\right).\left(\frac{1}{x}+\frac{1}{y}+\frac{1}{z}\right)-\frac{x+y+z}{x+y+z}=0\)

\(\Leftrightarrow\left(x+y+z\right).\left(\frac{1}{x}+\frac{1}{y}+\frac{1}{z}-\frac{1}{x+y+z}\right)=0\)

vì x+y+z khác 0 => \(\frac{1}{x}+\frac{1}{y}+\frac{1}{x}-\frac{1}{x+y+z}=0\)

\(\Leftrightarrow\frac{xy+yz+xz}{xyz}-\frac{1}{x+y+z}=0\)

\(\Leftrightarrow\frac{\left(xy+yz+xz\right).\left(x+y+z\right)-xyz}{xzy.\left(x+y+z\right)}=0\)

\(\Leftrightarrow\frac{x^2y+xy^2+xyz+zyx+y^2z+yz^2+x^2z+xyz+xz^2-xzy}{xyz.\left(x+y+z\right)}=0\)

\(\Leftrightarrow\left(x^2y+xyz\right)+\left(xy^2+y^2z\right)+\left(yz^2+xzy\right)+\left(x^2z+xz^2\right)=0\)

\(\Leftrightarrow xy.\left(x+z\right)+y^2.\left(x+z\right)+yz.\left(z+x\right)+xz.\left(x+z\right)=0\)

\(\Leftrightarrow\left(x+z\right).\left(xy+y^2+yz+xz\right)=0\)

\(\Leftrightarrow\left(x+z\right).\left[x.\left(y+z\right)+y.\left(y+z\right)\right]=0\)

\(\Leftrightarrow\left(x+y\right).\left(y+z\right).\left(x+z\right)=0\Leftrightarrow\orbr{\begin{cases}x=-y\\y=-z\end{cases}\text{hoặc }x=-z}\)

\(\Rightarrow P=\left(\frac{1}{x}-\frac{1}{y}\right).\left(\frac{1}{y}+\frac{1}{z}\right).\left(\frac{1}{z}+\frac{1}{x}\right)=0\)

ps: bài này t làm cách l8, ai có cách ez hơn giải vs ak :')  morongtammat

uk,đúng nhỉ!mik sorry

đề cần chứng minh nhỏ hơn 1 hay 11

nếu 1 thì

\(\frac{1}{2^2}+\frac{1}{3^2}+......+\frac{1}{100^2}\)

\(< \frac{1}{1\cdot2}+\frac{1}{2\cdot3}+.......+\frac{1}{99\cdot100}\)

\(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+......+\frac{1}{99}-\frac{1}{100}\)

\(=1-\frac{1}{100}< 1\)

\(\Rightarrowđcm\)

nếu nhỏ hơn 11 thì làm như thế thêm câu

vì đẳng thức trên <1<11

=>đcm

chỉ <1 thôi 

nhưng lần sau ghi cản thận vào

\(\frac{1}{2}+\frac{1}{2}\times\left(50\%+\frac{1}{4}\right)\)

\(=\frac{1}{2}+\frac{1}{2}\times\left(\frac{1}{2}+\frac{1}{4}\right)\)

\(=1\times\frac{3}{4}\)

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

1/2+1/2x(1/2+1/4)

=1/2+1/2x3/4

=1/2+3/8

=4/8+3/8=7/8

7/8 nhé 

7/2 + 7/2 x 9 =7/2 + 63/2

                   = 70/2 = 35

TI CK  cho mình nhé bạn 

7*9=63

\(\frac{7}{2}+\frac{7}{2}\cdot9=\frac{7}{2}+\frac{63}{2}=\frac{70}{2}=35\)