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BÀI 1

a) $\frac{7}{13}$ . $\frac{7}{15}$ - $\frac{5}{12}$ . $\frac{21}{39}$ + $\frac{49}{91}$ . $\frac{8}{15}$ 

= $\frac{7}{13}$ . $\frac{7}{15}$ - $\frac{5}{12}$ . $\frac{7}{13}$ + $\frac{7}{13}$ . $\frac{8}{15}$ 

= $\frac{7}{13}$ . ($\frac{7}{15}$ - $\frac{5}{12}$ + $\frac{8}{15}$)

= $\frac{7}{13}$ .$\frac{7}{12}$ 

= $\frac{49}{156}$ 

b) ($\frac{12}{199}$ + $\frac{23}{200}$ - $\frac{34}{201}$) . ($\frac{1}{2}$ - $\frac{1}{3}$ $\frac{1}{6}$)

= ($\frac{12}{199}$ + $\frac{23}{200}$ - $\frac{34}{201}$) . 0

= 0

BÀI 2:

a) 35 . 13 + 35 . 37 - 15 . 50

= 35 . (13 + 37) - 15 . 50

= 35 . 50 - 15 . 50

= 50 . (35 - 15)

= 50 . 20

= 50 . 2 . 10

= 100 . 10

= 1000

b) (2 . 9 + 9^3 . 45) :(9^3 . 10 - 9^3)

= [9. (2 . 9^2 . 45) : 9^4

= [9 . (2. 9^3 . 5)] : 9^4

= [9. (10 . 9^3)] : 9^4

= 9^4 . 10 : 9^4

= 10

c) 1968 : 16 + 5136 : 16 - 704 : 16

= (1968 + 5136 - 704) : 16 

= 6400 : 16

= 400

d) 2^3 . 5^3 - 3{400 - [673 - 2^3 . (7^8 : 7^6 + 7^0)]}

= (2 . 5)^3 - 3{400 - [673 - 8 . (7^2 + 1)]}

= 10^3 - 3{400 - [673 - 8 . (49 + 1)]}
= 1000 - 3[400 - (673 - 8 . 50)]

= 1000 - 3[400 - (673 - 400)]

= 1000 - 3(400 - 273)

= 1000 - 3 . 127

= 1000 - 381

= 619

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