Сравните значение выражения с дробью 7/39-{1/13}и 7/39 {2/3-1/3}

5x-7y

а) При x = 3/5, y = - 4/7

5*3/5-7 * (-4/7) =

=3 - (-4) = 3+4=7

5*3/5=5/1*3/5=3/1=3

7 * (-4/7) = 7/1 * (-4/7) = - 4/1=-4

б) при x = - 0,8, y = 0,6

5 * (-0,8) - 7*0,6=

=-4-4,2=-8,2

5

0,8

40

0

-4,0

7

*0,6

42

0

4,2

2.

а) 7/39 - (1/13 - 2/3) и 7/39 + (2/3 - 1/3)

10/13 > 20/39

1/13 - 2/3=3/39-26/39 = - 23/39

7/39 - (-23/39) = 7/39+23/39=30/39=10/13

2/3 - 1/3=1/3

7/39+1/3=7/39+13/39=20/39

б) 3/5 + 1/8:5/4 и (3/5 + 1.8) : 5.4

7/10 > 4/9

1/8:5/4=1/8*4/5=1/2*1/5=1/10

3/5+1/10=6/10+1/10=7/10

3/5 + 1.8=3/5+1 4/5=3/5+9/5=12/5=2 2/5

2 2/5:5,4=2 2/5:5 2/5=12/5:27/5=12/5*5/27=4/1*1/9=4/9