a/ \(=47^3+3.47^2.3+3.47.3^2+3^3\)

\(=\left(47+3\right)^3=50^3=125000\)

b/ \(=102^3-3.102^2.2+3.102.2^2-2^3\)

\(=\left(102-2\right)^3=100^3=1000000\)

\(\dfrac{3}{41}-\dfrac{12}{47}+\dfrac{27}{53}+\dfrac{4}{41}-\dfrac{16}{47}+\dfrac{36}{53}\)

\(=\left(\dfrac{3}{41}+\dfrac{4}{41}\right)-\left(\dfrac{12}{47}+\dfrac{16}{47}\right)+\left(\dfrac{27}{53}+\dfrac{36}{53}\right)\)

\(=\dfrac{7}{41}-\dfrac{28}{47}+\dfrac{63}{53}\)

\(=-\dfrac{819}{1927}+\dfrac{63}{53}\)

≃\(0,8\)

Suy ra 27-x=1

x=27-1

x=26

Vậyx=26

27 - x = 47 : 47

27 - x = 1

x = 27 - 1

x = 26

Answer : 26

47 . ( 27 - x ) = 47

       ( 27 - x ) = 47 : 47

         27 - x   = 1

               x   = 27 - 1

               x   = 26

Bạn tự giải

54 x 47 - 47 x 53 - 20 - 27

= 54 x 47 - 47 x 53 - 47

= 47 x (54-53-1)

= 47 x 0

= 0

54 x 47 - 47 x 53 - 20 - 27

= 47 x (54 - 53) - 20 - 27

= 47 x 1 - 20 - 27

= 47 - (20 + 27)

= 47 - 47

= 0

a, 85.(35-27)-35.(85-27)

=85.35-85.27-35.85+35.27

=85.27+35.27

=27.(85+35)

=27.120=3240

b, 47.(45-15)-47.(45+15)

=47.30-47.60

=47.(30-60)

=-1410

\(2b,\)\(54\times47-47\times53-20-27.\)

\(=47\times54-47\times53-47\)

\(=47\times\left(54-53-1\right)\)

\(=47\times0=0\)

\(2c,\)\(10000-47\times72-47\times28\)

\(=100\times100-47\times\left(72+28\right)\)

\(=100\times100-47\times100\)

\(=100\times\left(100-47\right)\)

\(=100\times53=5300\)

2b

54 x 47 - 47 x 53 - 20 - 27 = 47 x ( 54 - 53 ) - 20 - 27 = 47 - 20 - 27 = 47 - ( 20 + 27 ) = 47 - 47 = 0

2c

10000 - 47 x 72 - 47 x 28 = 10000 - 47 x ( 72 - 28 ) = 10000 - 47 x 44 = 10000 - 2068 = 7932