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\(a)\frac{11}{8}-\frac{7}{8}+\frac{3}{4}=\frac{4}{8}+\frac{3}{4}=\frac{2}{4}+\frac{3}{4}=\frac{5}{4}\)
\(b)\frac{24}{8}-\frac{5}{8}-3=(\frac{24}{8}-3)-\frac{5}{8}=3-3-\frac{5}{8}=-\frac{5}{8}\)
\(c)\)Tự làm
\(d)56\cdot78+8634=4368+8634=13002\)
Bài giải
a, \(\left(\frac{1}{6}+\frac{1}{10}+\frac{1}{15}\right)\text{ : }\left(\frac{1}{6}+\frac{1}{10}-\frac{1}{15}\right)=\left(\frac{5}{30}+\frac{3}{30}+\frac{2}{30}\right)\text{ : }\left(\frac{5}{30}+\frac{3}{30}-\frac{2}{30}\right)=\frac{1}{3}-\frac{1}{5}=\frac{2}{15}\)
b, \(\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{4}-\frac{1}{5}\right)\text{ : }\left(\frac{1}{4}-\frac{1}{5}\right)=\left(\frac{60}{120}-\frac{40}{120}+\frac{30}{120}-\frac{24}{120}\right)\text{ : }\left(\frac{5}{20}-\frac{4}{20}\right)=\frac{13}{60}\text{ : }\frac{1}{20}=\frac{13}{3}\)
Ta có :
a, \(\left(\frac{1}{6}+\frac{1}{10}+\frac{1}{15}\right)\text{ : }\left(\frac{1}{6}+\frac{1}{10}-\frac{1}{15}\right)=\left(\frac{5}{30}+\frac{3}{30}+\frac{2}{30}\right)\text{ : }\left(\frac{5}{30}+\frac{3}{30}-\frac{2}{30}\right)=\frac{1}{3}-\frac{1}{5}=\frac{2}{15}\)
b,
\(\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{4}-\frac{1}{5}\right)\text{ : }\left(\frac{1}{4}-\frac{1}{5}\right)=\left(\frac{60}{120}-\frac{40}{120}+\frac{30}{120}-\frac{24}{120}\right)\text{ : }\left(\frac{5}{20}-\frac{4}{20}\right)=\frac{13}{60}\text{ : }\frac{1}{20}=\frac{13}{3}\)
458 x 105 + 324 x 105
= 105 x ( 458 + 324)
= 105 x 782 = 82110
457 x 207 - 207 x 386
= 207 x ( 457 - 386)
= 207 x 71 = 14697
Thay \(a=\dfrac{16}{15}\) vào biểu thức ta được
\(\dfrac{3}{4}\) x \(\dfrac{16}{15}+\dfrac{6}{5}=\dfrac{4}{5}+\dfrac{6}{5}=\dfrac{4+6}{5}=\dfrac{10}{5}=2\)
Vậy với \(a=\dfrac{16}{15}\) giá trị biểu thức là 2
a) a*15+a*7
=25*15+25*7
=375+175=550
b56*78+8634
=4368+8634=13002
P/s: (*) là dấu nhân
\(\dfrac{15}{16}.\dfrac{8}{5}.\dfrac{3}{4}\)= \(\dfrac{5.3.4.2.3}{4.2.2.5.4}=\dfrac{9}{8}\)
= 120/80 x 3/4
=3/2 x3/4
=9/8