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1.43x7/31x7=301/217
59x13/7x13=767/217
=>767/217>301/217
hay59/13>43/31
2.rút gọn -48/224 còn -3/14
rút gọn -52/247 còn -4/19
-3/14=-3x19/14x19=-57/266
-4/19=-4x14/19x14=-56/266
=>-57/266<-56/266
hay-48/244<-52/247
vậy...
Bài 1
a) \(\dfrac{3}{8}+\dfrac{5}{8}=\dfrac{8}{8}=1\)
b) \(\dfrac{3}{4}+\dfrac{-7}{16}=\dfrac{12}{16}+\dfrac{-7}{16}=\dfrac{5}{16}\)
c) \(2\dfrac{17}{20}-\dfrac{1}{2}+3\dfrac{3}{20}=\dfrac{57}{20}-\dfrac{1}{2}+\dfrac{63}{20}\)\(=\dfrac{47}{20}+\dfrac{63}{20}=\dfrac{110}{20}=\dfrac{11}{2}\)
d) \(\dfrac{2}{3}-2\dfrac{1}{8}+\dfrac{7}{24}=\dfrac{2}{3}-\dfrac{17}{8}+\dfrac{7}{24}=\dfrac{16}{24}-\dfrac{51}{24}+\dfrac{7}{24}=\dfrac{16-51+7}{24}=\dfrac{-28}{24}=\dfrac{-7}{6}\)
Bài 2 :
a) \(x-\dfrac{7}{4}=3\)
\(x=3+\dfrac{7}{4}\)
\(x=\dfrac{19}{4}\)
b) \(x-\dfrac{1}{2}=\dfrac{4}{16}\cdot\dfrac{8}{3}\)
\(x-\dfrac{1}{2}=\dfrac{2}{3}\)
\(x=\dfrac{2}{3}+\dfrac{1}{2}\)
\(x=\dfrac{5}{6}\)
c) \(\dfrac{15}{11}\div x=\dfrac{45}{22}\)
\(x=\dfrac{15}{11}\div\dfrac{45}{22}\)
\(x=\dfrac{2}{3}\)
d) \(\dfrac{8}{3}-2x=\dfrac{8}{5}-1\)
\(\dfrac{8}{3}-2x=\dfrac{3}{5}\)
\(2x=\dfrac{8}{3}-\dfrac{3}{5}\)
\(2x=\dfrac{31}{15}\)
\(x=\dfrac{31}{15}\div2\)
\(x=\dfrac{31}{30}\)
a: MN=7+5=12cm
b: MK=12/2=6cm
OK=6-5=1cm
c: Vì OK<ON
nên K thuộc tia ON
a: MN=7+5=12cm
b: MK=12/2=6cm
OK=6-5=1cm
c: Vì OK<ON
nên K thuộc tia ON
\(\left(0,75-\frac{1}{4}\right):\frac{5}{6}=\left(\frac{3}{4}-\frac{1}{4}\right):\frac{5}{6}\)
\(=\frac{1}{2}:\frac{5}{6}=\frac{3}{5}\)
C1:(0,75-1/4):5/6
=(3/4-1/4):5/6
=1/2:5/6
=3/5
C2:(0,75-1/4):5/6
=(0,75-0,25). 6/5
=0,5.1,2
= 0.6
Bài 2: Đặt *=x
Số cần tìm sẽ có dạng là \(\overline{3x5}\)
\(\overline{3x5}⋮3\)
=>\(3+x+5⋮3\)
=>\(x+8⋮3\)
=>\(x\in\left\{1;4;7\right\}\)
=>*\(\in\left\{1;4;7\right\}\)
Bài 4:
a: 720;702;270;207;762;726;627;672;276;267
b: 762; 726; 627; 672; 276; 267