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\(a.=\frac{4}{13}\times\frac{13}{4}\times\frac{2}{3}\times\frac{3}{2}\)
\(=1\times1\)
\(=1\)
\(b.=\frac{19}{13}+\frac{7}{13}+\frac{14}{6}+\frac{4}{6}+\frac{1}{9}+\frac{17}{9}\)
\(=\frac{26}{13}+\frac{18}{6}+\frac{18}{9}\)
\(=2+3+2\)
\(=7\)
4/13 * 2/3 * 13/4* 3/2= (4/13 * 13/4 )* (2/3 * 3*2) = 1*1=1
19/13 + 14/6 + 1/9 + 4/6 + 7/13 + 17/9 = (19/13 + 7/13) + (14/6 + 4/6) + (1/9 + 17/9) = 2 + 3 + 2 =7
\(\dfrac{2}{3}+\dfrac{7}{13}-\dfrac{17}{9}+\dfrac{19}{13}-\dfrac{1}{9}+\dfrac{7}{3}\)
\(=\left(\dfrac{2}{3}+\dfrac{7}{3}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)-\left(\dfrac{17}{9}+\dfrac{1}{9}\right)\)
\(=\dfrac{9}{3}+\dfrac{26}{13}-\dfrac{18}{9}\)
\(=3+2-2\)
\(=3\)
(19+1)+(18+2)+(17+3)+(16+4)+(15+5)+(14+6)+(13+7)+(12+8)+(11+9)+20)+10
=20+20+20+20+20+20+20+20+20+20=(20*10)+10
=210
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20
=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+(10+20)
=20+20+20+20+20+20+20+20+20+30
=(20 x 9) + 30
=180 + 30
=210
tk nha
a) 47,54+18,72+5,13-17,54-7,72+4,87=(47,54-17,54)+(18,72-7,72)+(4,87+5,13)=30+11+10=51
b)4/7+7/13+17/9+19/13-8/9+17/7=(4/7+17/7)+(7/13+19/13)+(17/9-8/9)=3+2+1=6
14/6 + 1/9 + 19/13 + 17/9 + 7/13 + 4/6 = (14/6 + 4/6) + (1/9 + 17/9) + (19/13 + 7/13)
= 18/6 + 18/9 + 26/13
= 3 + 2 + 2
= 7
a: =9/13+4/13+2/9+7/9
=1+1
=2
b: =(44-17-23)/55
=4/55
c: =100+19,25
=119,25
d: =98,3-38
=60,3
a,
\(\frac{14}{6}+\frac{1}{9}+\frac{19}{13}+\frac{17}{9}+\frac{7}{13}+\frac{4}{6}\)
\(=\left(\frac{14}{6}+\frac{4}{6}\right)+\left(\frac{1}{9}+\frac{17}{9}\right)+\left(\frac{19}{13}+\frac{7}{13}\right)\)
\(=\frac{18}{6}+\frac{18}{9}+\frac{26}{13}\)
\(=3+2+2\)
\(=7\)
b,
\(\frac{995}{997}x\frac{990}{993}x\frac{997}{990}x\frac{993}{995}x\frac{97}{95}\)
\(=\frac{995x990x997x993x97}{997x993x990x995x95}\)
\(=\frac{97}{95}\)
(Cùng triệt tiêu 995 ; 990 ; 997 ; 993 )
\(=\frac{21.22.68}{11.17.63}=\frac{1.2.4}{1.1.3}=\frac{8}{3}\)
\(=\frac{5.7.26}{14.13.25}=\frac{1.1.2}{2.1.5}=\frac{1.1.1}{1.1.5}=\frac{1}{5}\)
\(\frac{13}{19}\times\left(\frac{19}{13}-\frac{7}{9}\right)\\ =\frac{13}{19}\times\frac{19}{13}-\frac{13}{19}\times\frac{7}{9}\)
\(=1-\frac{91}{171}\)
\(=\frac{80}{171}\)
Thấy đúng thì k đúng giúp mik
\(\frac{4}{6}+\frac{7}{13}+\frac{17}{9}+\frac{19}{13}+\frac{1}{9}+\frac{14}{6}\)
\(=\left(\frac{4}{6}+\frac{14}{6}\right)+\left(\frac{7}{13}+\frac{19}{13}\right)+\left(\frac{17}{9}+\frac{1}{9}\right)\)
\(=3+2+2=7\)
4/6 + 7/13 + 17/9 + 19/13 + 1/9 + 14/6. = ( 4/6 + 14/6 ) + ( 7/13 + 19/13 ) + ( 17/9 + 1/9 ). = 18/6 + 26/13 + 18/9. = 3 + 2 + 2 = 7.