a) 19,17x25x4=19,17(25x4)=19,17x100=1917

b)1,79x(8x125)=1,79x1000=1790

chúc bạn học tốt

Ta có

54,65 x 25,96 + 45,35 x 25,96

= 25,96 x ( 54,65 +45,35 )

=25,96 x 100

=2596

   54,65x25,96+45,25x25,96

=(54,65+45,35)x25,96

=100x25,96

=2596

54,65 x 25,96 + 45,35 x 25,96

=25,96x (54,65+45,35)

=25,96x 100

=2596

\(419:\left(8\times8\times4,18+0,17\times2,5+2,09\times2\times36+0,23\times2,5\right)\)

\(=419:\left(64\times4,18+0,17\times2,5+4,18\times36+0,23\times2,5\right)\)

\(=419:\left[\left(64+36\right)\times4,18+\left(0,17+0,23\right)\times2,5\right]\)

\(=419:\left[100\times4,18+0,4\times2,5\right]\)

\(=419:\left[418+1\right]\)

\(=419:419\)

\(=1\)

\(=\dfrac{419}{64\cdot4.18+0,17\cdot2,5+2,09\cdot72+0,23\cdot2,5}\)

\(=\dfrac{419}{0,4\cdot2,5+64\cdot4,18+2,09\cdot72}\)

\(=\dfrac{419}{1+418}=1\)

8×2145+1765×8-8×678

=17160+14120-5424

=31280-5424

=25856

= 8 x (2145 + 1765 - 678)

= 8 x 3232

= 25856

Mình sai r mình chưa đọc kĩ đề cho mình xl nhé..

b: =63x1000=63000

98 x 8 + 98 x 13 - 98

= 98 x ( 13 + 8 - 1 )

= 98 x 20

= 1960

125 x 63 x 8

= 63 x ( 125 x 8 )

= 63 x 1000

= 63000

56   x   63 9   x   8 = 7   x   8   x   7   x   9 9   x   8 = 7   x   7 = 49

7/8 x 1/4 + 7/8 x 2/4 + 7/8

=7/8 x\(\left(\dfrac{1}{4}+\dfrac{2}{4}\right)\) + 7/8

=7/8 x 3/4 + 7/8

=7/8 x \(\left(\dfrac{3}{4}+1\right)\)

=7/8 x 7/4

=49/32

`7/8 xx 1/4 + 7/8 xx 2/4 + 7/8`

`= 7/8 xx 1/4 + 7/8 xx 2/4 + 7/8xx1`

`= 7/8 xx (1/4 +2/4+1)`

`= 7/8 xx ( 3/4 + 4/4)`

`= 7/8 xx 7/4`

`= 49/32`

` @ nkhanh`

7/8 x 1/4 + 7/8 x 2/4 + 7/8

=7/8 x 1/4 + 7/8 x 2/4 + 7/8 x 4/4

= 7/8x(1/4+2/4+4/4)

=7/8x7/4

=49/32