# Math Help - Subsitution and elimination help

1. ## Subsitution and elimination help

Solve the linear systems using substitution

y=x+1
y=2x-4

y=x+1
y=2x-4

Solve the linear systems using elimination

6x+3y=27
-6x+2y=-2

4x+3y=21
4x-5y=29

Could someone please explain substitution and elimination for me, thanks for your help.

2. Originally Posted by LOL
Solve the linear systems using substitution

y=x+1
y=2x-4
Since y= x+1 in the first equation, substitute x+1 for y in the second equation: y= x+ 1= 2x- 4. Now solve x+ 1= 2x-4 for x and then use y= x+1 to get x.

y=x+1
y=2x-4
??? This is the same pair of equations!

Solve the linear systems using elimination

6x+3y=27
-6x+2y=-2
Adding the two equations eliminates x:
(6x+ 3y)+ (-6x+ 2y)= 27+ (-2)
(6x- 6x)+ (3y+ 2y)= 27- 2
5y= 25

Solve for y and then replace y by that number in either equation to find x.

4x+3y=21
4x-5y=29
Subtract one equation from the other:
(4x+3y)- (4x-5y)= 21- 29
(4x- 4x)+ (3y-(-5y)= 21- 29
8y= -8.

Could someone please explain substitution and elimination for me, thanks for your help.

3. Originally Posted by LOL
Could someone please explain substitution and elimination for me, thanks for your help.
Try some online lessons.