\(\text{7x- xy+ 2y= 18}\)

\(\Rightarrow xy-2y=7x-18\)

\(\Rightarrow y\left(x-2\right)=7x-18\)

\(\Rightarrow y=\dfrac{7x-18}{x-2}\)

\(=\dfrac{7x-14}{x-2}-\dfrac{4}{x-2}=7-\dfrac{4}{x-2}\)

\(x-2\in U\left(4\right)\) nếu \(y\in Z\)

Nếu x-2 = -2 \(\Rightarrow\) x = 0 ; y = 9
Nếu x-2 = -4 \(\Rightarrow\) x = -2 ; y = 8
Nếu x -2 = 2 \(\Rightarrow\) x = 4 ; y = 5
Nếu x-2 = 1 \(\Rightarrow\) x = 3 ; y = 3

Nếu x-2 = -1\(\Rightarrow\) x = 1 ; y = 11
Nếu x-2 = 4 \(\Rightarrow\) x = 6 ; y = 6

Nguyễn Thị Bích Thủy

Mấy thánh có ai nói em điên em cũng nhận hết nha:

\(\left(x+1\right)\left(x-2\right)< 0\)

\(\Leftrightarrow x+1< 0\Rightarrow x< -1\)

\(x-2>0\Rightarrow x>2\)

\(2< x< -1\)

\(x\in\left\{\varnothing\right\}\)

\(\Leftrightarrow x+1>0\Rightarrow x>-1\)

\(x-2< 0\Rightarrow x< 2\)

\(-1< x< 2\)

\(x\in\left\{0;1\right\}\)

\(-3xy+4y-6x=27\\ \Rightarrow-y\left(3x-4\right)-6x+8=35\\ \Rightarrow-y.\left(3x-4\right)-2\left(3x-4\right)=35\\ \Rightarrow\left(3x-4\right)\left(-y-2\right)=35\)

\(\Rightarrow3x-4=-1;-y-2=-35\)

hoặc \(3x-4=-5;-y-2=-7\)

hoặc \(3x-4=-7;-y-2=-5\)

hoặc \(3x-4=-35;-y-2=-1\)

hoặc \(3x-4=1;-y-2=35\)

hoặc \(3x-4=5;-y-2=7\)

hoặc \(3x-4=7;-y-2=5\)

hoặc \(3x-4=35;-y-2=1\)

\(\Rightarrow x=1;y=33\)

hoặc \(x=-\frac{1}{3};y=5\) ( loại vì x,y thuộc Z )

hoặc \(x=-1;y=3\)

hoặc \(x=-\frac{31}{3};y=-1\) ( loại vì x,y thuộc Z )

hoặc \(x=\frac{5}{3};y=-37\) ( loại vì x,y thuộc Z )

hoặc \(x=3;y=-9\)

hoặc \(x=\frac{10}{3};y=-7\) (loại vì x,y thuộc Z )

hoặc \(x=\frac{39}{3};y=-3\) ( loại vì x,y thuộc Z )

vậy \(\left(x,y\right)\in\left\{\left(1;33\right);\left(-1;3\right);\left(3;-9\right)\right\}\)

bài 1 Tính

a) \(1\frac{1}{3}\)X \(1\frac{1}{8}\)X \(1\frac{1}{15}\)X .............X \(1\frac{1}{99}\)

b) \(\left(1-\frac{1}{4}\right)\)X \(\left(1-\frac{1}{9}\right)\)X \(\left(1-\frac{1}{16}\right)\)X \(\left(1-\frac{1}{25}\right)\)X \(\left(1-\frac{1}{36}\right)\)

c) \(\left(\frac{99}{98}-\frac{98}{97}+\frac{1}{97x98}\right)\)

d) \(3\frac{1}{11}\)X \(\frac{27}{36}\)X \(1\frac{6}{7}\)X \(2\frac{4}{9}\)

Giúp mk nhé!

a) \(\left|2x\frac{1}{3}\right|+\frac{5}{6}=1\)

b)\(\frac{17}{2}-\left|2x-\frac{3}{4}\right|=-\frac{7}{4}\)

c) \(\frac{2}{3}x-\frac{3}{2}x=\frac{5}{12}\)

d) \(\frac{2}{5}+\frac{3}{5}.\left(3x-3,7\right)=-\frac{53}{10}\)

e) \(\frac{7}{9}:\left(2+\frac{3}{4}x\right)+\frac{5}{9}=\frac{23}{27}\)

f) \(\left(2\frac{4}{5}x-50\right):\frac{2}{3}=51\)

g)\(\left(x+\frac{1}{2}\right).\left(\frac{2}{3}-2x\right)=0\)

h)\(x.3\frac{1}{4}+\left(-\frac{7}{6}\right).x-1\frac{2}{3}=\frac{5}{12}\)

i)\(\frac{6}{2}=\frac{-5+x}{15}\)

k)\(\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+...+\frac{2}{x\left(x+1\right)}=\frac{2}{9}\)

tim x:

cau 1:\(\frac{x+1}{199}\)+\(\frac{x+2}{198}\)+\(\frac{x+3}{197}\)+\(\frac{x+4}{196}\)+\(\frac{x+5}{195}\)=(-5)

cau 2:\(\frac{1}{21}\)+\(\frac{1}{28}\)+\(\frac{1}{36}\)+....+\(\frac{2}{x\left(x+1\right)}\)=\(\frac{2}{9}\)