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a) \(\dfrac{3}{5}-\dfrac{3}{5}.\dfrac{2}{3}=\dfrac{3}{5}-\left(\dfrac{3}{5}.\dfrac{2}{3}\right)=\dfrac{3}{5}-\dfrac{2}{5}=\dfrac{1}{5}\)
b) \(\dfrac{-7}{9}.\dfrac{11}{15}-\dfrac{4}{15}.\dfrac{-7}{9}-\dfrac{7}{9}=\dfrac{-7}{9}.\left(\dfrac{11}{15}-\dfrac{4}{15}\right)-\dfrac{7}{9}=\dfrac{-7}{9}.\dfrac{7}{15}-\dfrac{7}{9}=-\dfrac{49}{135}-\dfrac{7}{9}=-\dfrac{154}{135}\)
d) \(3\dfrac{1}{7}-\left(4\dfrac{1}{2}+5\dfrac{3}{7}\right)=\dfrac{22}{7}-\left(\dfrac{9}{2}+\dfrac{38}{7}\right)=\dfrac{22}{7}-\left(\dfrac{63}{14}+\dfrac{76}{14}\right)=\dfrac{22}{7}-\dfrac{139}{14}=\dfrac{44}{14}-\dfrac{139}{14}=-\dfrac{95}{14}\)
tính giá trị biểu thức:A=4 phần 3 x 4 phần 7+4 phần 7 x 4 phần 11 +...........+4 phần 95 x 4 phần 99
4/3.4/7+4/7.4/11+...+4/95.4/99
=4/3.7+4/7.11+...+4/95.99
=1/3-1/7+1/7-1/11+...+1/95-1/99
=1/3-1/99
=32/99
a: -3/4x12=-36/4=-9
b: \(=\dfrac{7}{15}\cdot\dfrac{10}{21}=\dfrac{7}{21}\cdot\dfrac{10}{15}=\dfrac{1}{3}\cdot\dfrac{2}{3}=\dfrac{2}{9}\)
c: \(=\dfrac{7}{18}\cdot\dfrac{12}{21}=\dfrac{12}{18}\cdot\dfrac{7}{21}=\dfrac{2}{3}\cdot\dfrac{1}{3}=\dfrac{2}{9}\)
d: \(=\dfrac{11}{15}\cdot\dfrac{5}{22}=\dfrac{11}{22}\cdot\dfrac{5}{15}=\dfrac{1}{2}\cdot\dfrac{1}{3}=\dfrac{1}{6}\)
e: \(=-\dfrac{8}{15}\cdot\dfrac{5}{4}=\dfrac{-40}{60}=\dfrac{-2}{3}\)
f: \(=-15\cdot\dfrac{3}{5}=-9\)
A = 18/26 + -5/27 + -22/86 + 12/39 + -32/43
A = 9/13 + -5/27 + -11/43 + 4/13 + -32/43
A = -5/27 + ( 9/13 + 4/13 ) + ( -11/43 + -32/43 )
A = -5/27 + 1 + ( -1)
A = -5/27 + 0
A = 0
B = -10/12 + 8/15 + -19/56 + 3/-18 + 28/60
B = -5/6 + 8/15 + -19/56 + -1/6 + 7/15
B = -19/56 + ( -5/6 + -1/6 ) + ( 8/15 + 7/15 )
B = -19/56 + ( -1 ) + 1
B = -19/56 + 0
B = 0