Tính
117:{[79-3(33 -17)]:7+2}
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a)\(-\dfrac{2}{5}.\dfrac{4}{7}+\dfrac{-3}{5}.\dfrac{2}{7}+\dfrac{-3}{5}\)
=\(-\dfrac{2}{5}.\dfrac{4}{7}+\dfrac{3}{7}.\dfrac{-2}{5}+\dfrac{-3}{5}\)
=\(-\dfrac{2}{5}.\left(\dfrac{4}{7}+\dfrac{3}{7}\right)+\dfrac{-3}{5}\)
=\(\dfrac{-2}{5}.1+\dfrac{-3}{5}\)
=\(-\dfrac{2}{5}+\dfrac{-3}{5}\)
=\(-\dfrac{5}{5}\) = -1
\(\dfrac{5}{9}.\dfrac{14}{17}+\dfrac{1}{17}.\dfrac{5}{9}+\dfrac{2}{9}+\dfrac{5}{12}\)
=\(\dfrac{5}{9}.\left(\dfrac{14}{17}+\dfrac{1}{17}\right)+\dfrac{2}{9}+\dfrac{5}{12}\)
=\(\dfrac{5}{9}.\dfrac{15}{17}+\dfrac{2}{9}+\dfrac{5}{12}\)
=\(\dfrac{25}{51}+\dfrac{2}{9}+\dfrac{5}{12}\)
=\(\dfrac{691}{612}\)
117:{[79-3(3^3 -17)]:7+2}
=117:{[79-3(27-17)]:7+2}
=117:{[79-3.10]:7+2}
=117:{[79-30]:7+2}
=117:{49:7+2}
=117:{7+2}
=117:9
=13
a)=\(\frac{-2.4}{5.7}+\frac{-3.2}{5.7}+\frac{-3}{5}\)
=\(\frac{-2.4}{5.7}+\frac{-2.3}{5.7}+\frac{-3}{5}\)
=\(\frac{-2}{5}\left(\frac{4+3}{7}\right)+\frac{-3}{5}\)
=\(\frac{-2}{5}.1+\frac{-3}{5}\)
=-1
b)
80 - 4 . 52 + 3 .23=80 - 4 . 25 + 3 . 8=80 - 100 +24=-20+24=4
25 . 124 - 24 . 25 +212=24 .(124 - 25)+212=24 . 99 +212=2376 +212=2588
35 . 48 + 65 . 68 + 20 . 35=35 . (48 +20)+65 . 68=35 . 68 +65 . 68=68 . (35 + 65)=68 . 100=6800
27 :23+23.20-110=24+23- 1=16 + 8 -1=23
câu 3,câu 6,câu 7 mk ko làm đc vì ko biết cách viết dấu móc vuông với dấu móc kép nha bạn.:) ^_^
HOK TỐT
\(=117:\left[\left(79-3\cdot16\right):7+2\right]=117:\left[\left(79-48\right):7+2\right]\)
=117/5
117:{[79-3(33 -17)]:7+2}
=117:{[79-3.16]:7+2}
=117:{[79-48]:7+2}
=117:{31:7+2}
=117:{\(\dfrac{31}{7}\)+2}
=117:\(\dfrac{45}{7}\)
=\(\dfrac{91}{5}\)