Question

Daca se da proportia x/y = 2/7 ,determinati:
a) 4x/5y
b)x+y/x
c)y/y-x
d)2x+y/3y-5x

"/" inseamna supra

Answer 1

x/y=2/7 => x=2y/7 ....... inlocuiesti si => 2y/7/y=2/7 => y /7 =2/7 => y= 2 ×7 /2 = 7 .... y = 7 ..... => x=2 ...... .. 4x/5y = 4*2 /5*7 = 8/35 ..... x +y /x = 2+7/2 ...... y/y-× = 7 / 7-2 ...... 2×+y/3y-5x = 2*2 + 7 / 3*7 - 5*2 ....... eu nu le-am mai calculat ....

Answer 2

a)4x/5y=4/5*2/7=4*2/5*7=8/35
b)(x+y)/y=x/y+y/y=2/7+1=(2+7)/7=9/7
c)y/(y-x) inlocuim x=(2/7)y
 si avem y/(y-2y/7)=y/y(1-2/7)=1/(1-2/7)=1/[(7-2)/7]=1/(5/7)=7/5
d) folosim x=2y/7 si facem numaratorul intai : 2x+y=4y/7+y=(4y+7y)/7=11y/7
numitorul la fel: 3y-5*2y/7=3y-10y/7=(21y-10y)/7=11y/7
se observa ca cele 2 sunt egale
si la final avem numaratorul/numitor=(11y/7)/(11y/7)=1