a) \(\frac{7}{18}+\frac{4}{23}+\frac{11}{18}+\frac{19}{23}\)

\(=\left(\frac{7}{18}+\frac{11}{18}\right)+\left(\frac{4}{23}+\frac{19}{23}\right)\)

\(=1+1\)

\(=2\)

b) \(\frac{19}{15}+\frac{31}{23}-\frac{4}{15}-\frac{8}{23}\)

\(=\left(\frac{19}{15}-\frac{4}{15}\right)+\left(\frac{31}{23}-\frac{8}{23}\right)\)

\(=1+1\)

\(=2\)

ủng hộ tớ nha

a) (7/18+11/18)+(4/23+19/23)

=18/18+23/23

=1+1

=2

b)=2

\(a,b=2\)

\(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)

\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)

\(=\frac{5}{15}+\frac{12}{18}\)

\(=\frac{1}{3}+\frac{2}{3}\)

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

\(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)

\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)

\(=\frac{1}{3}+\frac{2}{3}\)

\(=1\)

\(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)

\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)

\(=\frac{5}{15}+\frac{12}{18}\)

\(=\frac{1}{3}+\frac{2}{3}\)

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

\(\Rightarrow=1\)

bn kia tính sai r kìa :vv

cách THCS:

\(\frac{2\times3\times6\times7}{2\times7\times18}=\frac{1\times1\times1\times1}{1\times1\times1}=1\)

Ta có: 3/7=24/56>14/56=2/8>1/8

=>3/7>1/8

C1: Ta có: \(\frac{3}{7}=\frac{24}{56};\frac{1}{8}=\frac{7}{56}\)

Mà \(\frac{24}{56}>\frac{7}{56}\)

\(\Rightarrow\frac{3}{7}>\frac{1}{8}\)

C2: Ta có: \(\frac{3}{7}>\frac{1}{7}\)(so sánh 2 PS cùng mẫu)

                \(\frac{1}{8}<\frac{1}{7}\)(so sánh 2 PS cùng tử)

\(\Rightarrow\frac{3}{7}>\frac{1}{7}>\frac{1}{8}\)

\(\Rightarrow\frac{3}{7}>\frac{1}{8}\)

a.\(\dfrac{18}{15}+\dfrac{7}{15}+\dfrac{12}{15}=\dfrac{18+7+12}{15}=\dfrac{37}{15}\)

b.\(\dfrac{9}{7}+\dfrac{8}{7}+\dfrac{11}{7}=\dfrac{9+8+11}{7}=\dfrac{28}{7}=4\)

\(\frac{3}{7}x\frac{25}{19}-\frac{1}{7}x\frac{18}{19}\)

\(=\left(\frac{3}{7}-\frac{1}{7}\right)x\left(\frac{25}{19}-\frac{18}{19}\right)\)

\(=\frac{2}{7}x\frac{7}{19}\)

\(=\frac{14}{133}\)

3/7×25/19-2/7×18/19

75/133-36-133

39/133