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a, Ta có : \(-\frac{21}{28}=-\frac{3}{4}=-\frac{3.13}{4.13}=-\frac{39}{52}\)
b, Đề sai .
c, Ta có : \(-\frac{1111}{2222}=-\frac{1.1111}{2.1111}=-\frac{1}{2}\)
d, Ta có : \(\frac{-131313}{-171717}=\frac{131313}{171717}=\frac{13.10101}{17.10101}=\frac{13}{17}\)
e, Ta có : \(\frac{a}{b}=\frac{a.\left(-1\right)}{b.\left(-1\right)}=\frac{-a}{-b}\)
f, Ta có : \(\frac{-a}{b}=-\frac{a}{b}=\frac{a}{-b}\)
Mình xin lỗi! Câu b là: \(\frac{54}{270}\)=\(\frac{1}{5}\)
a) \(\frac{5252}{7575}=\frac{52}{75};\frac{525252}{757575}=\frac{52}{75}\)
Vậy cả 3 phân số trên bằng nhau
b) \(\frac{1313}{1515}=\frac{13}{15};\frac{131313}{151515}=\frac{13}{15}\)
Vậy các phân số trên bằng nhau
\(\frac{52}{73}=\frac{52\cdot101}{73\cdot101}=\frac{5252}{7373}\)
\(\frac{52}{73}=\frac{52\cdot10101}{73\cdot10101}=\frac{525252}{737373}\)
1) A = \(\frac{-15}{19}.\frac{23}{37}+\frac{14}{37}.\frac{15}{19}=\frac{15}{19}.\frac{-23}{37}+\frac{14}{37}.\frac{15}{19}=\frac{15}{19}.\left(\frac{-23}{37}+\frac{14}{37}\right)=\frac{15}{19}.\frac{-9}{37}=\frac{-135}{703}\)
\(a)\) Ta có :
\(\frac{51}{85}=\frac{3}{5}\)
\(\frac{58}{145}=\frac{2}{5}\)
Vì \(\frac{3}{5}>\frac{2}{5}\) nên \(\frac{51}{85}>\frac{58}{145}\)
Vậy \(\frac{51}{85}>\frac{58}{145}\)
\(b)\) Ta có :
\(\frac{69}{-230}=\frac{-3}{10}\)
\(\frac{-39}{143}=\frac{-3}{11}\)
Vì \(\frac{-3}{10}< \frac{-3}{11}\) nên \(\frac{69}{-230}< \frac{-39}{143}\)
Vậy \(\frac{69}{-230}< \frac{-39}{143}\)
\(c)\) Ta có :
\(1+\frac{-7}{41}=\frac{34}{41}\)
\(1+\frac{13}{-47}=\frac{34}{47}\)
Vì \(\frac{34}{41}>\frac{34}{47}\) nên \(1+\frac{-7}{41}>1+\frac{13}{-47}\) hay \(\frac{-7}{41}>\frac{13}{-47}\)
Vậy \(\frac{-7}{41}>\frac{13}{-47}\)
\(d)\) Ta có :
\(1-\frac{40}{49}=\frac{9}{49}\)
\(\frac{15}{21}=\frac{5}{7}=\frac{35}{49}< \frac{40}{49}\)
Vậy \(\frac{40}{49}>\frac{15}{21}\)
a) \(\frac{31}{23}-\left(\frac{7}{23}+\frac{8}{23}\right)\)
\(=\frac{31}{23}-\frac{15}{23}\)
\(=\frac{16}{23}\)
b) \(\left(\frac{1}{3}+\frac{12}{67}+\frac{13}{41}\right)-\left(\frac{79}{67}-\frac{28}{41}\right)\)
\(=\frac{1}{3}+\frac{12}{67}+\frac{13}{41}-\frac{79}{67}+\frac{28}{41}\)
\(=\frac{1}{3}+\left(\frac{12}{67}-\frac{79}{67}\right)+\left(\frac{13}{41}+\frac{28}{41}\right)\)
\(=\frac{1}{3}+\frac{-67}{67}+\frac{41}{41}\)
\(=\frac{1}{3}-1+1\)
\(=\frac{1}{3}\)
c) \(\frac{38}{45}-\left(\frac{8}{45}-\frac{17}{52}-\frac{3}{11}\right)\)
\(=\frac{38}{45}-\frac{8}{45}+\frac{17}{52}+\frac{3}{11}\)
\(=\frac{30}{45}+\frac{17}{52}+\frac{3}{11}\)
\(=\frac{2}{3}+\frac{17}{52}+\frac{3}{11}\)
\(=\frac{104+51}{156}+\frac{3}{11}\)
\(=\frac{155}{156}+\frac{3}{11}\)
\(=\frac{156}{156}-\frac{1}{156}+\frac{3}{11}\)
\(=1-\frac{1}{156}+\frac{3}{11}\)
\(=1-\left(\frac{11-468}{1716}\right)\)
\(=1-\frac{-457}{1716}\)
\(=1+\frac{457}{1716}\)
\(=\frac{2173}{1716}\)
a)31/23-(7/32+8/23)=31/23-7/32-8/23=(31/23-8/23)-7/32=1-7/32=25/32
1/ ĐÁP ÁN:
\(\frac{-9}{33}=\frac{3}{-11}\); \(\frac{15}{9}=\frac{5}{3}\); \(\frac{-12}{19}=\frac{60}{-95}\)
2/ ĐÁP ÁN:
\(\frac{-7}{20}=\frac{3}{-18}=\frac{-9}{54}\ne\frac{12}{18}=\frac{-10}{-15}\ne\frac{14}{20}\)
3/ ĐÁP ÁN:
\(\frac{2}{3}=\frac{40}{60}\); \(\frac{3}{4}=\frac{45}{60}\); \(\frac{4}{5}=\frac{48}{60}\); \(\frac{5}{6}=\frac{50}{60}\)