Question

stiind ca x/y=0,75, calculati:
a) (y-x)/(x+y)
b) 3x+y/5y-4x
c)y*y-x*x/x*x+y*y

Answer 1

x /y = 75/100 = 3/4          ⇒  x /3 = y /4 = k     ⇒  x = 3k   si y = 4k 
a) (y-x)/(x+y) = ( 4k - 3k) / ( 3k +4k ) = k / 7k = 1/7
b) 3x+y/5y-4x  = ( 9k  + 4k ) / ( 20k - 12k ) = 13k / 8k = 13 / 8 
c)y*y-x*x/x*x+y*y = ( 16k² - 9 k ² ) / ( 9k² + 16 k² ) = 7 k² / 25k² = 7 / 25