Giai giup mk
a) (-2,5) . (-7,5) . (-4)
b)\(1\frac{4}{23}+\frac{8}{21}-\frac{4}{23}+0,6+\frac{13}{21}\)
c)\(\frac{2}{7}.15\frac{1}{3}-\frac{2}{7}.20\frac{1}{3}+4\frac{1}{3}\)
d)\(2\frac{1}{4}:\left(\frac{-3}{5}\right)-1\frac{1}{4}:\left(\frac{-3}{5}\right)\)
a) ( -2.5 ) . ( 7,5) .( -4 )
= [(-2,5).(-4)].(7,5)
= 10 . 7,5
= 75
b) \(1\frac{4}{23}+\frac{8}{21}-\frac{4}{23}+0,6+\frac{13}{21}\)
=\(1\frac{4}{23}-\frac{4}{23}+\frac{8}{21}+\frac{13}{21}-0,6\)
\(=1+1-0,6\)
\(=2-0,6\)
= 1,4
c) \(\frac{2}{7}.15\frac{1}{3}-\frac{2}{7}.20.\frac{1}{3}+4\frac{1}{3}\)
\(=\frac{2}{7}.5-\frac{1}{3}.\frac{40}{7}+4\frac{1}{3}\)
= \(=\frac{10}{7}-\frac{17}{7}\)
= -1
d) \(2\frac{1}{4}:\left(\frac{-3}{5}\right)-1\frac{1}{4}:\left(\frac{-3}{5}\right)\)
\(=\frac{9}{4}.\left( \frac{-5}{3}\right)-\frac{5}{4}.\left(\frac{-5}{3}\right)\)
=\(\left(\frac{-5}{3}\right).\left(\frac{9}{4}-\frac{5}{4}\right)\)
\(=\frac{-5}{3}.1\)
\(=\frac{-5}{3}\)