Вычислите : а)3/7+4/9; б)17/18 -11/12; в) 7/9+4/15; г) 1/8+4/9; д) 8/9-7/8; е) 7/16+1/6; ж)9/14+37-1/28; з)9/11-2/5; и)13/15-2/3; к)5/6+2/9; л)1/6+1/4-1/8; м) 13/16+9/32; н)20/21+4/7; о)10/21+9/14; п) 1/3-1/6+1/4; р)3/28+5/14.

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Ответ:

Кица234

06.10.2020 02:28

а) $\tt\displaystyle\frac{3}{7}+\frac{4}{9}=\frac{3*9}{7*9}+\frac{4*7}{9*7}=\frac{27}{63}+\frac{28}{63}=\frac{55}{63}\\$

б) $\tt\displaystyle\frac{17}{18}-\frac{11}{12}=\frac{17*2}{18*2}-\frac{11*3}{12*3}=\frac{34}{36}-\frac{33}{36}=\frac{1}{36}\\$

в) $\tt\displaystyle\frac{7}{9}+\frac{4}{15}=\frac{7*5}{9*5}+\frac{4*3}{15*3}=\frac{35}{45}+\frac{12}{45}=\frac{47}{45}=1\frac{2}{45}\\$

г) $\tt\displaystyle\frac{1}{8}+\frac{4}{9}=\frac{1*9}{8*9}+\frac{4*8}{9*8}=\frac{9}{72}+\frac{32}{72}=\frac{41}{72}\\$

д) $\tt\displaystyle\frac{8}{9}-\frac{7}{8}=\frac{8*8}{9*8}-\frac{7*9}{8*9}=\frac{64}{72}-\frac{63}{72}=\frac{1}{72}\\$

е) $\tt\displaystyle\frac{7}{16}+\frac{1}{6}=\frac{7*3}{16*3}+\frac{1*8}{6*8}=\frac{21}{48}+\frac{8}{48}=\frac{29}{48}\\$

ж) $\tt\displaystyle\frac{9}{14}+\frac{3}{7}-\frac{1}{28}=\frac{9*2}{14*2}+\frac{3*4}{7*4}-\frac{1}{28}=\frac{18}{28}+\frac{12}{28}-\frac{1}{28}=\frac{29}{28}=1\frac{1}{28}\\$

з) $\tt\displaystyle\frac{9}{11}-\frac{2}{5}=\frac{9*5}{11*5}-\frac{2*11}{5*11}=\frac{45}{55}-\frac{22}{55}=\frac{23}{55}\\$

и) $\tt\displaystyle\frac{13}{15}-\frac{2}{3}=\frac{13}{15}-\frac{2*5}{3*5}=\frac{13}{15}-\frac{10}{15}=\frac{3}{15}=\frac{3*1}{3*5}=\frac{1}{5}\\$

к) $\tt\displaystyle\frac{5}{6}+\frac{2}{9}=\frac{5*3}{6*3}+\frac{2*2}{9*2}=\frac{15}{18}+\frac{4}{18}=\frac{19}{18}=1\frac{1}{18}\\$

л) $\tt\displaystyle\frac{1}{6}+\frac{1}{4}-\frac{1}{8} =\frac{1*4}{6*4}+\frac{1*6}{4*6}-\frac{1*3}{8*3}=\frac{4}{24}+\frac{6}{24}-\frac{3}{24}=\frac{10}{24}-\frac{3}{24}=\frac{7}{24}\\$

м) $\tt\displaystyle\frac{13}{16}+\frac{9}{32}=\frac{13*2}{16*2}+\frac{9}{32}=\frac{26}{32}+\frac{9}{32}=\frac{35}{32}=1\frac{3}{32}\\$

н) $\tt\displaystyle\frac{20}{21}+\frac{4}{7}=\frac{20}{21}+\frac{4*3}{7*3}=\frac{20}{21}+\frac{12}{21}=\frac{32}{21}=1\frac{11}{21}\\$

о) $\tt\displaystyle\frac{10}{21}+\frac{9}{14}=\frac{10*2}{21*2}+\frac{9*3}{14*3}=\frac{20}{42}+\frac{27}{42}=\frac{47}{42}=1\frac{5}{42}\\$

п) $\tt\displaystyle\frac{1}{3}-\frac{1}{6}+\frac{1}{4}=\frac{1*4}{3*4}-\frac{1*2}{6*2}+\frac{1*3}{4*3}=\frac{4}{12}-\frac{2}{12}+\frac{3}{12}=\frac{5}{12}\\$