Question

Algebra.Exercitiul 14 coroana + 15 puncte.

Answer 1

a/b = 2/5 => a = 2b/5

7a + 8b)/(14a - 5b) =

= (14b/5 + 8b)/(28b/5 - 5b)

= (54b/5)/(3b/5)

= 54b/5×5/3b

= 18

Answer 2

Explicație pas cu pas:

a / b = 2 / 5

a = 2b / 5

( 7a + 8b ) / ( 14a  - 5b ) =

= ( 7 · 2b / 5 + 8b ) / ( 14 · 2b / 5 - 5 b )

= ( 14b / 5 + 8b ) / ( 28b / 5  - 5b )

= ( 14b / 5 + 40b / 5 ) / ( 28b / 5 - 25 b / 5 )

= ( 54b / 5 ) / ( 3b / 5 )

= ( 54 b / 5 )  · ( 5 / 3b ) ( simplificăm 5 cu 5 şi 5 cu 54 )

= 18