Question

Rezolvati sistemele: a) 2x-1 totul supra 3 + y+4 totul supra 5=2 3x-y=x+2y+1

Answer 1

[(2x-1)/(3+y+4)]/5=2⇒   (2x-1)/(7+y)=2·5
(2x-1)/(7+y)=10
2x-1=10(7+y)
2x-1=70+10y
2x-10y=70+1
2x-10y=71

3x-y=x+2y+1
3x-x-y-2y=1
2x-3y=1

avem sistemul
{2x-10y=71
{2x-3y=1           inmultim -1

{2x-10y=71
{-2x+3y=-1
2x-2x-10y+3y=71-1
-7y=70       inmultim -1
7y=70
y=70/7
y=10
din 2x-3y=1 rezulta 2x-3·10=1
2x=1+30
x=31/2
x=15,5