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a,
Ta có:
\(\dfrac{3}{7}=1-\dfrac{4}{7}\)
\(\dfrac{11}{15}=1-\dfrac{4}{15}\)
So sánh phân số \(\dfrac{4}{7}\) và \(\dfrac{4}{15}\)
Vì \(7< 15\) nên \(\dfrac{1}{7}>\dfrac{1}{15}\)
\(\Rightarrow1-\dfrac{4}{7}< 1-\dfrac{4}{15}\)
Vậy \(\dfrac{3}{7}< \dfrac{11}{15}\)
b)
\(\dfrac{-11}{6}< -1< \dfrac{-8}{9}\) nên \(\dfrac{-11}{6}< \dfrac{-8}{9}\)
c)
\(\dfrac{305}{25}=\dfrac{305:5}{25:5}=\dfrac{61}{5}\)
Ta có:
Mẫu số chung 2 phân số: 80
\(\dfrac{297}{16}=\dfrac{297*5}{16*5}=\dfrac{1485}{80}\)
\(\dfrac{61}{5}=\dfrac{61*16}{5*16}=\dfrac{976}{80}\)
Vì \(1485>976\) nên\(\dfrac{1485}{80}>\dfrac{976}{80}\)
Vậy \(\dfrac{297}{16}>\dfrac{305}{25}\)
d,
$\frac{-205}{317}=\frac{-205:-1}{317:-1}=\frac{205}{-317}$
Ta có:
Mẫu số chung 2 phân số: -35187
\(\dfrac{205}{-317}=\dfrac{205*111}{-317*111}=\dfrac{22755}{-35187}\)
\(\dfrac{-83}{111}=\dfrac{-83*-317}{111*-317}=\dfrac{26311}{-35187}\)
Vì \(22755< 26311\) nên\(\dfrac{22755}{-35187}< \dfrac{26311}{-35187}\)
Vậy \(\dfrac{-205}{317}< \dfrac{-83}{111}\)
Câu d, mình làm sai, cho mình sửa lại:
\(\dfrac{-205}{317}=\dfrac{-22755}{35187}\)
\(\dfrac{-83}{111}=\dfrac{-26311}{35187}\)
Vậy là \(-22755>-26311\) hay \(\dfrac{-205}{317}>\dfrac{-83}{111}\)
a: -3/100=-9/300; -2/3=-200/300
=>-3/100>-2/3
b: -3/5=-9/15
-2/3=-10/15
=>-3/5>-2/3
c: -5/4<-1<-3/8
d: -2/3=-8/12; -3/4=-9/12
=>-2/3>-3/4
e: -267/268>-1
-1>-1347/1343
=>-267/268>-1347/1343
Mấy bài dễ tự làm nhé:D
1)
Đặt: \(\dfrac{a}{b}=\dfrac{c}{d}=k\Leftrightarrow\left\{{}\begin{matrix}a=bk\\c=dk\end{matrix}\right.\)
\(\left\{{}\begin{matrix}\dfrac{a}{a+b}=\dfrac{bk}{bk+b}=\dfrac{bk}{b\left(k+1\right)}=\dfrac{k}{k+1}\\\dfrac{c}{c+d}=\dfrac{dk}{dk+d}=\dfrac{dk}{d\left(k+1\right)}=\dfrac{k}{k+1}\end{matrix}\right.\)
Ta có điều phải chứng minh
\(\left\{{}\begin{matrix}\dfrac{a}{a-b}=\dfrac{bk}{bk-b}=\dfrac{bk}{b\left(k-1\right)}=\dfrac{k}{k-1}\\\dfrac{c}{c-d}=\dfrac{dk}{dk-d}=\dfrac{dk}{d\left(k-1\right)}=\dfrac{k}{k-1}\end{matrix}\right.\)
Ta có điều phải chứng minh
a) \(2.04:\left(-3.12\right)=\dfrac{204}{-312}=\dfrac{-17}{26}\)
b) \(\left(-1\dfrac{1}{2}\right):1.25=\dfrac{-3}{2}:\dfrac{5}{4}=\dfrac{-3}{2}\cdot\dfrac{4}{5}=\dfrac{-12}{10}=\dfrac{-6}{5}\)
c) \(4:5\dfrac{3}{4}=4:\dfrac{23}{4}=4\cdot\dfrac{4}{23}=\dfrac{16}{23}\)
d) \(10\dfrac{3}{7}:5\dfrac{3}{14}=\dfrac{73}{7}:\dfrac{73}{14}=\dfrac{2}{1}\)
a) 3/8 = 1/8 + 2/8 = 1/8 + 1/4
3/8 = 5/8 - 2/8 = 5/8 - 1/4
b) 5/12 = 1/12 + 4/12 = 1/12 + 1/3
5/12 = 7/12 - 2/12 = 7/12 - 1/6
c) 1/11 = -2/11 + 3/11
1/11 = 2/11 - 1/11
d) 1/4 = -2/4 + 3/4 = -1/2 + 3/4
1/4 = 5/4 - 4/4 = 5/4 -1
a) \(3,7:4,5=\dfrac{3,7}{4,5}=\dfrac{37}{45}\)
b) \(2\dfrac{1}{3}:4\dfrac{2}{3}=\dfrac{7}{3}:\dfrac{14}{3}=\dfrac{7}{3}\times\dfrac{3}{14}=\dfrac{1}{2}\)
c) \(\dfrac{3}{8}:0,7=\dfrac{3}{8}:\dfrac{7}{10}=\dfrac{3}{8}\times\dfrac{10}{7}=\dfrac{15}{28}\)
d) \(5\dfrac{1}{7}:2\dfrac{1}{3}=\dfrac{36}{7}:\dfrac{7}{3}=\dfrac{36}{7}\times\dfrac{3}{7}=\dfrac{108}{49}\)
a, -5/7 là âm
b,4/-9 là âm