Question

ex 1 urgentttttttttttt

Answer 1

a)  5 / 6 + 1 / 9 = ( 3 x 5 ) / 18 + ( 2 x 1 ) / 18 = 15 / 18 + 2 / 18 = 17 / 18

→ cel mai mic multiplu comun al numitorilor 6 si 9 = 18

→ amplific fractia 5 / 6 cu 3 si fractia 1 / 9 cu 2

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b ) 2 / 3 + ( -  1 / 4 ) = 2 / 3 - 1 / 4 = 8 / 12 - 3 / 12 = 5 / 12

c)  - 5 / 12 - 3 / 16 = - 20 / 48 -  9 / 48 = - 29 / 48

d)   - 3 / 10 - 4 / 15 = - 9 / 30 - 8 / 30 = - 17 / 30

e)   9 / 20 - 8 / 16 = 9 / 20 - 1 / 2 = 9 / 20 - 10 / 20 = - 1 / 20

f)    1 / 2 + 1 / 3 - 1 / 4 = 6 / 12 + 4 / 12 - 3 / 12 = ( 10 - 3 ) / 12 = 7 / 12

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g)    2 / 21 - 13 / 42 + 1 / 70 = 2 / 21 - 1 / 4 + 1 / 70 = 40 / 420 - 130 / 420 + 6 / 420 =

= ( - 90 + 6 ) / 420 = - 84 / 420 = - 21 / 105

21 = 3 x 7

4 = 2²

70 = 2 x 5 x 7

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cmmmc al numitorilor 21;  4   si 70 = 2² x 3 x 5 x 7 = 420

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h)   13 / 36 + 1 / 9 - 5 / 9 =  13 / 36 + 4 / 36 - 20 / 36 = - 3 / 36 = - 1 / 12

i)    3 + 1 / 2 = 6 / 2 + 1 / 2 = 7 / 2 = 3 intregi si 1 / 2

j)   4 / 3 + 0 = 4 / 3

k )    1 / 7 - 4 / 3 + 6 / 7 + 1 / 3 = ( 1 / 7 + 6 / 7 ) - ( 4 / 3 - 1 / 3 ) = 7 / 7 - 3 / 3 = 1 - 1 = 0

l )    100 / 200 + 101 / 303 + 50 / 300 =

= 1 / 2 + 1 / 3 + 1 / 6 = ( 3 + 2 + 1 ) / 6 = 6 / 6 = 1

m )   3 intregi si 3 / 4 = ( 3 x 4 + 3 ) / 4 = 15 / 4

3 intregi si 1 / 4 = ( 3 x 4+ 1 ) / 4 = 13 / 4

15 / 4 - 13 / 4 = 2 / 4 = 1 / 2