Question

Ex 2,3 si 4 va rog..

Answer 1

Răspuns:

2.a) x=10%

  b) 20

3. x=1

4. (x+2y)/(3x-y)=1

Explicație pas cu pas:

2.

a) 400 ......100%

    40  .........x  ⇒x=40·100/400=40/4=10%  x=10%

b) (65/100)·x=130  ⇒65x=13000  ⇒x=13000/65=200

10%·200=(10/100)·200=10·200/100=20    ⇒20 este 10% din 200

3.

(x+2)/(x+5)=1/2  ⇒2(x+2)=x+5  ⇒2x+4=x+5  ⇒2x-x=5-4  ⇒x=1

4.

x/4y=3/8  ⇒8x=12y  ⇒x=12y/8=3y/2   x=3y/2

Se inlocuieste valoarea lui x in relatia (x+2y)/(3x-y). ⇒

(x+2y)/(3x-y)=[(3y/2)+2y]/[(3·3y/2-y]=[(3y+4y)/2]/{(9y-2y)/2)=7y/2/7y/2=(7y/2)·(2/7y)=(7y·2)/(2·7y)=1