98 x 103 x 98 - 98 x 2

= 98 x ( 103 x 98 - 2 )

= 98 x 10092

= 989016

bạn ơi, đáng lẽ đề là thế này mới đúng

98 x 103 - 98 - 98 x 2

= 98 x ( 103 - 1 - 2 )

= 98 x 100

= 9800

98 x 103 x 98 - 98 x 2

= 98 x (103 + 1 - 2)

= 98 x 102

= 98 x (100 + 2)

= 98 x 100 + 98 x 2

= 9800 + 196

= 9996

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

A = (1 - 1/95) . ( 1 - 1/96) . (1 - 1/97) . (1 - 1/98) . ( 1 - 1/99)
A =  94/95 . 95/96 . 96/97 . 97/98 . 98/99 
A = \(\dfrac{94.95.96.97.98}{95.96.97.98.99}\)
A = 94/99 
Vậy A = 94/99 
 - HokTot - 

\(A=\left(1-\dfrac{1}{95}\right)\times\left(1-\dfrac{1}{96}\right)\times\left(1-\dfrac{1}{97}\right)\times\left(1-\dfrac{1}{98}\right)\times\left(1-\dfrac{1}{99}\right)\)

\(A=\dfrac{94}{95}\times\dfrac{95}{96}\times\dfrac{96}{97}\times\dfrac{97}{98}\times\dfrac{98}{99}\)

\(A=\dfrac{94\times95\times96\times97\times98}{95\times96\times97\times98\times99}\)

\(A=\dfrac{94}{99}\) (gạch bỏ những số giống nhau)

bỏ 1 ra ngoài lấy 94/95.95/96.96/97.97/98.98.99=94/99 vậy a là 94/99

a, 98x8+98x13-98

=98x8+98x13-98x1

=98x[8+13-1]

=98x20

=1960

b,125x63x8

=[125x8]x63

=1000x63

=63000

a) Tính bằng cách thuận tiện nhất:

134 x 4 x 5

= 134 x (4 x 5)

= 134 x 20 = 1680

5 x 36 x 2

= 36x (5 x 2)

= 36 x 10 = 360

42 x 2 x 7 x5

= (42 x 7) x (2 x5)

= 294 x 10 = 2940

b) 137 x 3 + 137 x 97

= 137 x (3 + 97)

= 137 x 100 = 13700

94 x 12 + 94 x 88

= 94 x (12 + 88)

= 94 x 100 = 9400

428 x 12 - 428 x 2

= 428 x (12 - 2) = 4280

537 x 39 - 537 x 19

= 537 x (39 - 19)

= 537 x 20 = 10740

=452.(17+98-15)

=452.100

=45200

=452 x(17+98-15)

=452 x 100

=45200

\(452\times17+452\times98-452\times15\)
\(\Rightarrow452\times\left(17+98-15\right)\)
\(\Rightarrow452\times100\)
\(\Rightarrow45200\)

16 x 98 + 16 x 2

= 16 x ( 98 + 2 )

= 16 x 100

= 1600

16 x 98 + 16 x 2

= 16 x ( 98 + 2 ) 

= 16 x 100 = 1600

= 16 x (98+2)

=16 x 100=1600