SOLUTION: I need help in solving the system of equations by elimination. 1. 2x-y=3; x+2y=-1 2. x+2y=-4; 2x-3y=1 3. Solve the system of equations by substitution. 3x+y=3; y=-x-3 How do

Hi, 

solving a system of equations by elimination

Example: Note: the process is to eliminate one of the variables

 2x- y = 3  

  x+2y = -1

Multiply both sides of the equation by 2 to eliminate the y varaible

 4x- 2y = 6 

  x+ 2y = -1

Add:

5x = 5  Solve for x and substitute into one of the original equations to find y

x = 1  (2-y = 3)  y = -1  check your answers using one of the equations



Solve a system of equations by substitution

Ex: 3x+y=3; y=-x-3

substituting y=-x-3 for y

3x + (-x-3)=3    

2x = 6  

x = 3  substitute value for x into y = -x -3,  y = -6

check your answers using one of the equations



solve  system of equations by graphing

read from graph where the two lines intersect:  Pt(2,4)

check your answer by substituting the ordered pair into one of the equations

ex: y=2x; y=x+2