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Bài 1:
1: =15+37+52-37-17=52-2=50
2: =38-42+14-25+27+15=62-42+29=20+29=49
Bài 1: Bỏ ngoặc rồi tính
3) (21-32) - (-12+32)=21-32-(-12)-32=21-32+12-32=-31
4) (12+21) - (23-21+10)=12+21-23+21-10=21
5) (57-725) - (605-53)=57-725-605+53=-1220
6) (55+45+15) - (15-55+45)=55+45+15-15+55-45=55+55=110
Bài 2: Tính các tổng sau một cách hợp lí
1) (-37) + 14 + 26 + 37=(-37+37)+(14+26)=0+40=40
2) (-24) +6 + 10 + 24=(-24+24)+(6+10)=0+16=16
3) 15 + 23 + (-25) + (-23)=(15-25)+(23-23)=-10+0=-10
4) 60 + 33 + (-50) + (-33)=(60-50)+(33-33)=10+0=10
5) (-16) + (-209) + (-14) + 209=(-16-14)+(-209+209)=-30+0=-30
6) (-12) + (-13) + 36 + (-11)=(-11-12-13)+36=-36+36=0
\(1,=38-42+14-25+27+15=27\)
\(2,=12+21-23+21-10=21\)
\(3,=57-725-605+53=-1220\)
\(4,=55+45+15-15+55-45=110\)
Rút gọn rồi tính:
a) \(\frac{8}{10}-\frac{12}{9}+\frac{10}{15}\)
\(=\frac{4}{5}-\frac{4}{3}+\frac{2}{3}\)
\(=\frac{12-20+10}{15}\)
\(=\frac{2}{15}\)
b) \(\left(\frac{20}{16}-\frac{15}{12}\right)\div\left(\frac{6}{8}-\frac{9}{12}\right)\)
\(=\left(\frac{5}{4}-\frac{5}{4}\right)\div\left(\frac{3}{4}-\frac{3}{4}\right)\)
\(=1\div1\)
\(=1\)
\(a,\frac{8}{10}-\frac{12}{9}+\frac{10}{15}\)
\(=\frac{4}{5}-\frac{4}{3}+\frac{2}{3}\)
\(=\frac{4}{5}-\left(\frac{4}{3}+\frac{2}{3}\right)\)
\(=\frac{4}{5}-2\)
\(=\frac{4}{5}+\frac{-10}{5}\)
\(=\frac{-6}{5}\)
\(b,\left(\frac{20}{16}-\frac{15}{12}\right):\left(\frac{6}{8}-\frac{9}{12}\right)\)
\(=\left(\frac{5}{4}-\frac{5}{4}\right):\left(\frac{3}{4}-\frac{3}{4}\right)\)
\(=0:0\)
\(=0\)
`a) ((-14).15)/(21.(-10))`
`=(-7.3.5.3)/(7.3.(-2).5)`
`=3/2`
`b) ((-7).12)/((-16).(-14))`
`=(-7.3.2.2)/(-2.2.2.(-7).2)`
`=(-3)/4`
`c) ((-11).(-5))/(15.22) `
`=(-11.(-5))/(3.5.11.2)`
`=1/6`
`d) ((-10).(-18))/((-6).25.7)`
`=(-5.2.-2.3.3)/(-2.3.5.5.7)`
`=6/35`
`e) (5.7-7.9)/(7.2+6.7)`
`=(7.(5-9))/(7.(2+6))`
`=-4/8`
`=-1/2`
`f) (11.9-22.3)/(33.2)`
`=(33.(3-2))/(33.2)`
`=1/2`
a/ =15+37+52-37-17
=(15+52)-17+(37-37)
=67-17+0
=50
b/=38-42+14-25+27+15
=-4+14+27-25+15
=10+27-40
=37-40
=-3
c/=-21+32+12-32
=-21+12+32-32
=11+0
=11
d/=-12-21+23-23+21-10
=-33+0+11
=-22
e/=57-725-605+53
=-668-605+53
=-1273+53
=-1220
f/=55+45+15-15+55-45
=55+55+45-45+15-15
=110+0+0
=110
12/15 = 4/5 15/10 = 3/2
14/21 = 2/3 70/20 = 7/2
18/12 = 3/2 55/66 = 5/6
( 4/5 - 2/3 - 3/2 ) : ( 3/2 - 7/2 - 5/6 ) = -41/30 : -17/6
= 41/85