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a)
(1/3-1/5)x1/4 = 1/3x1/4-1/5x1/4=1/12-1/20=1/30
(1/3-1/5)x1/4 = 2/15x1/4=1/30
b)
2/5 x 3/7 + 2/5 x 4/7= 6/35 + 8/35 = 14/35 = 2/5
2/5 x 3/7 + 2/5 x 4/7= (3/7+4/7) x 2/5 = 1 x 2/5 = 2/5
a: C1: (1/3-1/5)*1/4
=2/15*1/4=2/60=1/30
C2: (1/3-1/5)*1/4
=1/3*1/4-1/5*1/4
=1/12-1/20=1/30
b: C1: 2/5*3/7+2/5*4/7
=6/35+8/35=14/35=2/5
C2: 2/5*3/7+2/5*4/7
=2/5(3/7+4/7)
=2/5*1=2/5
\(\dfrac{3}{5}+\dfrac{4}{3}\times\dfrac{5}{6}=\dfrac{3}{5}+\dfrac{10}{9}=\dfrac{27}{45}+\dfrac{50}{45}=\dfrac{77}{45}\)
\(2-\dfrac{7}{6}+\dfrac{1}{3}=\dfrac{12}{6}-\dfrac{7}{6}+\dfrac{2}{6}=\dfrac{7}{6}\)
\(\dfrac{7}{6}\times3-\dfrac{3}{5}=\dfrac{7}{2}-\dfrac{3}{5}=\dfrac{35}{10}-\dfrac{6}{10}=\dfrac{29}{10}\)
3-(3/4+x-1/3):2/3=1/2
3-(3/4+x-1/3)=1/2*2/3
3-(3/4+x-1/3)=2/6
3/4+x-1/3=3-2/6
3/4+x-1/3=8/3
3/4+x=8/3+1/3
3/4+x=3
x=3-3/4
x=9/4
4/3 + 3/3 = 7/3
5/2 x 4 = 10
2 - 7/8 = 16/8 - 7/8 = 9/8
5 x 7/5 = 7
5/6 x 7/2= 35/12
4/3 + 3/3 = 7/3
5/2 x 4 = 10
2 - 7/8 = 16/8 - 7/8 = 9/8
5 x 7/5 = 7
5/6 x 7/2= 35/12
\(=\dfrac{3}{7}\cdot\left(\dfrac{4}{9}+\dfrac{5}{9}+1\right)=\dfrac{3}{7}\cdot2=\dfrac{6}{7}\)
\(=\dfrac{3}{7}\times\dfrac{4}{9}\times\dfrac{5}{9}\times\dfrac{3}{7}+\dfrac{3}{7}=\dfrac{3}{7}\times\left(\dfrac{4}{9}+\dfrac{5}{9}+1\right)=\dfrac{3}{7}\times2=\dfrac{6}{7}\)
5/9 : 3/x+2 = 5/3 ( Câu này mình để x + 2 dưới mẫu nhé còn nếu tách chuyển vế âm lớp 4 chưa học ! )
<=> 3/x+2 = 5/9 : 5/3
<=> 3/x+2 = 1/3
<=> x + 2 = 9 <=> x = 7
3/7 + x/35 = 4/5
<=> x/35 = 4/5 - 3/7 = 13/35
<=> x = 13
\(\frac{3}{4}\times x=\frac{5}{7}\)
\(x=\frac{5}{7}:\frac{3}{4}\)
\(x=\frac{20}{21}\)