\(\frac{3}{9}+\frac{9}{15}+\frac{8}{12}=\frac{1}{3}+\frac{3}{5}+\frac{2}{3}=\left(\frac{1}{3}+\frac{2}{3}\right)+\frac{3}{5}=1+\frac{3}{5}=\frac{8}{5}\)

\(\frac{4}{10}+\frac{12}{32}+\frac{9}{15}=\frac{2}{5}+\frac{3}{8}+\frac{3}{5}=\left(\frac{2}{5}+\frac{3}{5}\right)+\frac{3}{8}=1+\frac{3}{8}=\frac{11}{8}\)

\(\left(\frac{4}{10}-\frac{8}{30}\right)\times\frac{6}{8}=\frac{2}{15}\times\frac{3}{4}=\frac{6}{60}=\frac{1}{10}\)

a, 3/9+9/15+8/12=1/3+3/5+2/3=14/15+2/3=8/5

Rút gọn rồi tính:

a) \(\frac{8}{10}-\frac{12}{9}+\frac{10}{15}\)

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

\(=\frac{12-20+10}{15}\)

\(=\frac{2}{15}\)

b) \(\left(\frac{20}{16}-\frac{15}{12}\right)\div\left(\frac{6}{8}-\frac{9}{12}\right)\)

\(=\left(\frac{5}{4}-\frac{5}{4}\right)\div\left(\frac{3}{4}-\frac{3}{4}\right)\)

\(=1\div1\)

\(=1\)

\(a,\frac{8}{10}-\frac{12}{9}+\frac{10}{15}\)

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

\(=\frac{4}{5}-\left(\frac{4}{3}+\frac{2}{3}\right)\)

\(=\frac{4}{5}-2\)

\(=\frac{4}{5}+\frac{-10}{5}\)

\(=\frac{-6}{5}\)

\(b,\left(\frac{20}{16}-\frac{15}{12}\right):\left(\frac{6}{8}-\frac{9}{12}\right)\)

 \(=\left(\frac{5}{4}-\frac{5}{4}\right):\left(\frac{3}{4}-\frac{3}{4}\right)\)

\(=0:0\)

\(=0\)

a: \(\dfrac{15}{8}-\dfrac{13}{8}=\dfrac{15-13}{8}=\dfrac{2}{8}=\dfrac{1}{4}\)

b: \(\dfrac{7}{15}-\dfrac{2}{15}=\dfrac{7-2}{15}=\dfrac{5}{15}=\dfrac{1}{3}\)

c: \(\dfrac{11}{12}-\dfrac{2}{12}=\dfrac{11-2}{12}=\dfrac{9}{12}=\dfrac{3}{4}\)

d: \(\dfrac{19}{7}-\dfrac{5}{7}=\dfrac{19-5}{7}=\dfrac{14}{7}=2\)

Tham khảo :

^{(Tại mik lười ko mún ghi nên bạn tham khảo cái ảnh này nhá)}

Tham khảo :

Mình vừa học xong 

mn ơi e vít nhầm là tính rồi rút gọn mn sửa lại là rút gọn rùi tính

a: =2/5+3/5=1

b: =1/3+2/3=1

c: =7/8+5/8=12/8=3/2

d: =2/7+3/7=5/7

\(a,\dfrac{2}{5}+\dfrac{3}{5}=\dfrac{5}{5}=1\\ b,\dfrac{1}{3}+\dfrac{2}{3}=\dfrac{3}{3}=1\\ c,\dfrac{7}{8}+\dfrac{5}{8}=\dfrac{12}{8}=\dfrac{3}{2}\\ d,\dfrac{1}{7}+\dfrac{3}{7}=\dfrac{4}{7}\)

a: \(\dfrac{3}{9}\times\dfrac{5}{4}=\dfrac{5}{4}\times\dfrac{1}{3}=\dfrac{5\times1}{4\times3}=\dfrac{5}{12}\)

b: \(\dfrac{10}{15}\times\dfrac{3}{5}=\dfrac{3}{5}\times\dfrac{2}{3}=\dfrac{3\times2}{5\times3}=\dfrac{2}{5}\)

c: \(\dfrac{5}{8}\times\dfrac{4}{12}=\dfrac{5}{8}\times\dfrac{1}{3}=\dfrac{5}{3\times8}=\dfrac{5}{24}\)

d: \(\dfrac{9}{27}\times\dfrac{3}{21}=\dfrac{1}{7}\times\dfrac{1}{3}=\dfrac{1\times1}{7\times3}=\dfrac{1}{21}\)