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\(\frac{3}{4}+\frac{7}{8}=\frac{12}{16}+\frac{14}{16}=\frac{12+14}{16}=\frac{28}{16}=\frac{7}{4}\)
\(\frac{12}{3}-\frac{5}{12}=\frac{48}{12}-\frac{5}{12}=\frac{45}{12}=\frac{15}{4}\)
Rút gọn ta được: \(\frac{1}{4}=\frac{1}{4}=\frac{1}{4}=\frac{1}{4}=0,25\)
a) \(A=\frac{27\text{x}45+27\text{x}25}{2+4+6+8+...+18}=\frac{27\left(45+25\right)}{\left(18+2\right)\text{x}\left(\frac{18-2}{2}+1\right)}\)
\(A=\frac{27\text{x}70}{20\text{x}9}=\frac{3\text{x}9\text{x}10\text{x}7}{10\text{x}2\text{x}9}\)
\(A=\frac{21}{2}\)
b) \(B=\frac{28\text{x}108-52\text{x}12}{32-28+24-20+16-12+8-4}\)
\(B=\frac{28\text{x}12\text{x}9\text{}\text{}-52\text{x}12}{\left(32-28\right)+\left(24-20\right)+\left(16-12\right)+\left(8-4\right)}\)
\(B=\frac{12\left(28\text{x}9-52\right)}{4+4+4+4}=\frac{12\text{x}200}{4\text{x}4}\)
\(B=\frac{4\text{x}3\text{x}4\text{x}50}{4\text{x}4}=150\)
12/5 -4/5 =8/5
11/6 -2/3 =21/18 =7/6
7/8 -2/7 =33/56
4 -8/5 =20/5-8/5 =12/5
2 -3/8 =16/8 -3/8 =13/8
16/7 -2 =16/7 -14/7 =2/7
25/4 -3=25/4 -12/4 =13/4
câu 2 : câu 3 :
a) 8/5 a)4 - 8/5 = 20/5 - 8/5 =12/5
b) 7/6 b)2 - 3/8 =16/8 - 3/8 = 13/8
c) 35/56 c)16/7 - 2 = 16/7 - 14/7 = 2/7
d)25/4 - 3 = 25/4 - 12/4 = 13/4







\(\frac{8}{12}\cdot\frac{18}{8}-\frac34\cdot\frac{8}{12}\)
\(=\frac{8}{12}\cdot\left(\frac{18}{8}-\frac34\right)=\frac23\cdot\left(\frac94-\frac34\right)=\frac23\cdot\frac64=\frac{12}{12}=1\)
éo hiểu luôn