Question

Exercițiul 15 si 16
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Answer 1

15) 
2x/3y =4/9 ⇒18 x = 12y ⇒ x/y = 12/18 = 2/3

x/y = 2/3 ⇒ x  = 2y/3;  y = 3x/2

3x/5y = (3×2) / ( 5×3)  = 6/15 = 2/5;

( 2y - x) / ( 3y + x ) = ( 2·3x/2 - x)  / ( 3· 3x/2 + x) = (3x - x) / ( 9x/2 + 2x/2)=
= 2x × 2/11x = 4/11

16)  (8a+3b) / 2b = 7/4 ⇒  4(8a+3b) = 14b
32a + 12 b =14b
32a = 14 - 12b
32a = 2b ⇒ 16 a = b⇒ a/b = 1/16  ⇒ a = b/16, iar b = 16a

(b² - a²) /15ab = ( 16²a²- b²/16²) / (15× b/16 × 16a) = [(16²)²a² - b²] / 16²  : 15ab=
=( 16⁴a