Question

20 Rezolvati prin metoda substitutiei următoarele sisteme de ecuatii

d. {4(x+5)-2=5(y+3)
{-x+2(y+4)=11

e. {2(x+4)=-3(y-5)
{x=2(y+1)-16

f. {2y=4-3x
{-3x=y+1

VA ROG, AM NEVOIE ACUM REPEDE, IAR CINE RASPUNDE PRIMUL II DAU COROANA, JUR!​

Answer 1

Răspuns:

$\left \{ {{4x+20-2 -5y=15} \atop {-x+2y+8=11} \right.$     $\left \{ {{4x-5y=-3} \atop {-x+2y=3}} \right.$    => x=2y-3

4*(2y-3)-5y=-3    8y-12- 5y=-3    3y=12-3=9

y=9:3=3   y= 3    x=2*3-3=6-3=3  Solutie x=3  y=3

e) $\left \{ {{2x+8+3y =15} \atop {x= 2y+2-16}} \right.$  $\left \{ {{2x +3y=15-8} \atop {x=2y-14}} \right.$  

2* (2y-14)+ 3y=7     4y -28+3y=7

7y=7+28=35    y=35:7 =5   y=5

x=2*5-14=10-14= - 4    x= -4     Solutie x=-4  y=5