Question

Dau 25 de puncte va rog urgent


a=7x+15
b=5x+35
a|b, b|a
x=?

Answer 1

Răspuns:

b | a <=> 5x+35 | 7x+15  |*5

              5x+35 | 5x+35 |*7

<=> 5x+35 | 5*(7x+15)

      5x+35 | 7*(5x+35)

<=> 5x+35 | 35x+75

      5x+35 | 35x+245

<=> 5x+35 | (35x+245) -(35x+75)

<=> 5x+35 | (245-75)

<=> 5x+35| 170 => 5x| 135 <=> x|27 => x ∈ D₂₇= {1;3;9;27}

a | b => 7x+15 | 5x+35  |*7

            7x+15 | 7x+15    |*5

<=> 7x+15| 35x+245

      7x+15| 35x+75

<=> 7x+15| diferenta- 170 => 7x|155 <=> x| 155/7 => x∉N