2 và 2/5 x 25/18=12/5 x 25/18=10/3

9/11 : 2 và 5/2 x 2 và 3/4=9/11 : 9/2 x 11/4

                                          =2/11 x 11/4

                                          =1/2

Bài 2: 

a: 2/5=14/35

3/7=15/35

b: -3/4=-9/12

-7/-12=7/12

c: 5/9=60/108

-11/-12=11/12=99/108

d: -4/7=-36/63

8/9=56/63

-10/21=-30/63

Bài 2: 

a: 2/5=14/35

3/7=15/35

b: -3/4=-9/12

-7/-12=7/12

c: 5/9=60/108

-11/-12=11/12=99/108

d: -4/7=-36/63

8/9=56/63

-10/21=-30/63

a) 3+15+35+63           = 116

18+90+210+378            378

=58/189

a) \(\frac{1.3+3.5+5.7+7.9}{3.6+9.10+15.14+21.18}\)

= \(\frac{1.3+3.5+5.7+7.9}{1.3.2.3+3.5.2.3+5.7.2.3+7.9.2.3}\)

= \(\frac{1.3+3.5+5.7+7.9}{1.3.6+3.5.6+5.7.6+7.9.6}\)

= \(\frac{1.3+3.5+5.7+7.9}{6.\left(1.3+3.5+5.7+7.9\right)}=\frac{1}{6}\)

Dấu "." là dấu nhân cấp 2 

b)  \(\frac{1.2+2.3+3.4+4.5}{3.6+6.9+9.12+12.15}\)

= \(\frac{1.2+2.3+3.4+4.5}{1.2.3.3+2.3.3.3+3.4.3.3+4.5.3.3}\)

= \(\frac{1.2+2.3+3.4+4.5}{1.2.9+2.3.9+3.4.9+4.5.9}\)

= \(\frac{1.2+2.3+3.4+4.5}{9.\left(1.2+2.3+3.4+4.5\right)}=\frac{1}{9}\)

Dấu "." là dấu nhân cấp 2 

c) \(\frac{0,3+\frac{3}{7}+\frac{3}{11}}{0,4+\frac{4}{7}+\frac{4}{11}}\)= \(\frac{\frac{3}{10}+\frac{3}{7}+\frac{3}{11}}{\frac{4}{10}+\frac{4}{7}+\frac{4}{11}}\)= \(\frac{3.\left(\frac{1}{10}+\frac{1}{7}+\frac{1}{11}\right)}{4.\left(\frac{1}{10}+\frac{1}{7}+\frac{1}{11}\right)}=\frac{3}{4}\)

a) \(\frac{1.3+3.5+5.7+7.9}{3.6+9.10+15.14+21.18}=\frac{1.3+3.5+5.7+7.9}{1.3.2.3+3.3.5.3+3.5+2.7+3.7+3.9}=\frac{1.3+3.5+5.7+7.9}{2.3\left(1.3+3.5+5.7+7.9\right)}=\frac{1}{6}\)

b)\(\frac{1.2+2.3+3.4+4.5}{3.6+6.9+9.12+12.15}\)

Con này làm tương tự như con a

c) \(\frac{\frac{3}{10}+\frac{3}{7}+\frac{3}{11}}{\frac{4}{10}+\frac{4}{7}+\frac{4}{11}}=\frac{3.\left(\frac{1}{10}+\frac{1}{7}+\frac{1}{11}\right)}{4.\left(\frac{1}{10}+\frac{1}{7}+\frac{1}{11}\right)}=\frac{3}{4}\)

Chúc học tốt

a) \(x+\frac{4}{5}=\frac{3}{2}\)

\(\Rightarrow x=\frac{3}{2}-\frac{4}{5}\)

\(\Rightarrow x=\frac{7}{10}\)

Vậy \(x=\frac{7}{10}.\)

b) \(x-\frac{3}{2}=\frac{11}{4}\)

\(\Rightarrow x=\frac{11}{4}+\frac{3}{2}\)

\(\Rightarrow x=\frac{17}{4}\)

Vậy \(x=\frac{17}{4}.\)

c) \(\frac{25}{3-x}=\frac{5}{6}\)

\(\Rightarrow\left(3-x\right)5=25.6\)

\(\Rightarrow15-5x=150\)

\(\Rightarrow5x=15-150\)

\(\Rightarrow5x=-135\)

\(\Rightarrow x=-135:5\)

\(\Rightarrow x=-27\)

Vậy \(x=-27.\)

ai giúp mình câu c đi

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