Em cần làm gì vơi biểu thức này em ơi???

Nó còn tùy từng trường hợp cụ thể của đề bài chứ em?

1: \(\left(\dfrac{1,5+1-0,75}{2,5+\dfrac{5}{3}-1,25}+\dfrac{0,375-0,3+\dfrac{3}{11}+\dfrac{3}{12}}{-0,625+0,5-\dfrac{5}{11}-\dfrac{5}{12}}\right):\dfrac{1890}{2005}+115\)

\(=\left(\dfrac{3\left(\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}\right)}{5\left(\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}\right)}+\dfrac{3\left(\dfrac{1}{8}-\dfrac{1}{10}+\dfrac{1}{11}+\dfrac{1}{12}\right)}{-5\left(\dfrac{1}{8}-\dfrac{1}{10}+\dfrac{1}{11}+\dfrac{1}{12}\right)}\right)\cdot\dfrac{2005}{1890}+115\)

\(=0\cdot\dfrac{2005}{1890}+115=115\)

2: \(\dfrac{\dfrac{1}{9}-\dfrac{1}{7}-\dfrac{1}{11}}{\dfrac{4}{9}-\dfrac{4}{7}-\dfrac{4}{11}}+\dfrac{0,6-\dfrac{3}{25}-\dfrac{3}{125}-\dfrac{3}{625}}{\dfrac{4}{5}-0,16-\dfrac{4}{125}-\dfrac{4}{625}}\)

\(=\dfrac{\dfrac{1}{9}-\dfrac{1}{7}-\dfrac{1}{11}}{4\left(\dfrac{1}{9}-\dfrac{1}{7}-\dfrac{1}{11}\right)}+\dfrac{3\left(\dfrac{1}{5}-\dfrac{1}{25}-\dfrac{1}{125}-\dfrac{1}{625}\right)}{4\left(\dfrac{1}{5}-\dfrac{1}{25}-\dfrac{1}{125}-\dfrac{1}{625}\right)}\)

\(=\dfrac{1}{4}+\dfrac{3}{4}=1\)

3: \(564\left(\dfrac{12+\dfrac{12}{7}-\dfrac{12}{25}-\dfrac{12}{71}}{4+\dfrac{4}{7}-\dfrac{4}{25}-\dfrac{4}{71}}:\dfrac{3+\dfrac{3}{13}+\dfrac{3}{19}+\dfrac{3}{101}}{5+\dfrac{5}{13}+\dfrac{5}{19}+\dfrac{5}{101}}\right)\)

\(=564\left(\dfrac{12\left(1+\dfrac{1}{7}-\dfrac{1}{25}-\dfrac{1}{71}\right)}{4\left(1+\dfrac{1}{7}-\dfrac{1}{25}-\dfrac{1}{71}\right)}:\dfrac{3\left(1+\dfrac{1}{13}+\dfrac{1}{19}+\dfrac{1}{101}\right)}{5\left(1+\dfrac{1}{13}+\dfrac{1}{19}+\dfrac{1}{101}\right)}\right)\)

\(=564:\left(3\cdot\dfrac{5}{3}\right)=564\cdot5=2820\)

4: \(\dfrac{155-\dfrac{10}{7}-\dfrac{5}{11}+\dfrac{5}{23}}{402-\dfrac{26}{7}-\dfrac{13}{11}+\dfrac{13}{23}}+\dfrac{\dfrac{3}{5}+\dfrac{3}{13}-0,9}{\dfrac{7}{91}+0,2-\dfrac{3}{10}}\)

\(=\dfrac{5\left(31-\dfrac{2}{7}-\dfrac{1}{11}+\dfrac{1}{23}\right)}{13\left(31-\dfrac{2}{7}-\dfrac{1}{11}+\dfrac{1}{23}\right)}+\dfrac{\dfrac{3}{5}+\dfrac{3}{13}-\dfrac{9}{10}}{\dfrac{1}{13}+\dfrac{1}{5}-\dfrac{1}{10}}\)

\(=\dfrac{5}{13}+\dfrac{3\left(\dfrac{1}{5}+\dfrac{1}{13}-\dfrac{1}{10}\right)}{\dfrac{1}{5}+\dfrac{1}{13}-\dfrac{1}{10}}=\dfrac{5}{13}+3=\dfrac{44}{13}\)

5: \(\dfrac{0,375-0,3+\dfrac{3}{11}+\dfrac{3}{12}}{-0,625+0,5-\dfrac{5}{11}-\dfrac{5}{12}}+\dfrac{1,5+1-0,75}{2,5+\dfrac{5}{3}-1,25}\)

\(=-\dfrac{\dfrac{3}{8}-\dfrac{3}{10}+\dfrac{3}{11}+\dfrac{3}{12}}{\dfrac{5}{8}-\dfrac{5}{10}+\dfrac{5}{11}+\dfrac{5}{12}}+\dfrac{\dfrac{3}{2}+\dfrac{3}{3}-\dfrac{3}{4}}{\dfrac{5}{2}+\dfrac{5}{3}-\dfrac{5}{4}}\)

\(=-\dfrac{3\left(\dfrac{1}{8}-\dfrac{1}{10}+\dfrac{1}{11}+\dfrac{1}{12}\right)}{5\left(\dfrac{1}{8}-\dfrac{1}{10}+\dfrac{1}{11}+\dfrac{1}{12}\right)}+\dfrac{3\left(\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}\right)}{5\left(\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}\right)}\)

\(=-\dfrac{3}{5}+\dfrac{3}{5}=0\)

a: Vì OA và OB là hai tia đối nhau

nên O nằm giữa A và B

=>AB=OA+OB=6+2=8(cm)

b: I là trung điểm của AB

=>\(IA=IB=\dfrac{AB}{2}=4\left(cm\right)\)

Vì AI<AO

nên I nằm giữa A và O

=>AI+IO=AO

=>IO+4=6

=>IO=2(cm)

=>OA=3IO

c: Các góc đỉnh O có trên hình là \(\widehat{xOt};\widehat{xOz};\widehat{xOy};\widehat{tOz};\widehat{tOy};\widehat{zOy}\)

TH1:

5x+10=0

5x=-10

x=-2

Th2:

2x-10=0

2x=10

x=5

Vậy x thuộc tập hợp -2 và 5

Ta có: GH//JI

=>\(\widehat{JGH}+\widehat{GJI}=180^0\)(hai góc trong cùng phía)

=>\(\widehat{JGH}=180^0-90^0=90^0\)

ta có: GH//JI

=>\(\widehat{HIJ}=\widehat{xHI}\)(hai góc so le trong)

=>\(\widehat{HIJ}=47^0\)

a: |2,5|+|7,5|=2,5+7,5=10

b: \(1,2\cdot\left|-3\right|+6,4=1,2\cdot3+6,4=3,6+6,4=10\)

c: \(\left|-\dfrac{7}{2}\right|+\left|\dfrac{15}{2}\right|=\dfrac{7}{2}+\dfrac{15}{2}=\dfrac{22}{2}=11\)

Đặt \(A=\left(1-\dfrac{2}{42}\right)\left(1-\dfrac{2}{56}\right)\left(1-\dfrac{2}{72}\right)...\left(1-\dfrac{2}{2652}\right)\)

\(=\left(1-\dfrac{2}{6.7}\right)\left(1-\dfrac{2}{7.8}\right)\left(1-\dfrac{2}{8.9}\right)...\left(1-\dfrac{2}{51.52}\right)\)

Ta có:

\(1-\dfrac{2}{n\left(n+1\right)}=\dfrac{n\left(n+1\right)-2}{n\left(n+1\right)}=\dfrac{n^2+n-2}{n\left(n+1\right)}=\dfrac{\left(n-1\right)\left(n+2\right)}{n\left(n+1\right)}\)

Do đó:

\(A=\dfrac{5.8}{6.7}.\dfrac{6.9}{7.8}.\dfrac{7.10}{8.9}...\dfrac{50.53}{51.52}\)

\(=\dfrac{5.6.7...50}{6.7.8...51}.\dfrac{8.9.10...53}{7.8.9...52}=\dfrac{5}{51}.\dfrac{53}{7}=\dfrac{265}{357}\)