Question 12161
Substitution method:


y=-3x-18
5x-2y=-8


Second equation:
5x - 2(______) = -8

5x - 2(-3x-18)=-8
5x + 6x + 36 = -8
11x + 36 = -8
11x + 36-36 = -8 - 36
11x = -44
x= -4


Substitute back into the first equation to find y:
y= -3x - 18
y= -3(-4) - 18
y=12 - 18 = -6


Substitute both answers into the second equation for a check:
5x-2y= -8
5(-4)-2(-6)= -8
-20+12 = -8  
It checks!




Elimination method:


3x-2y=1
-6x+4y=-2

In order to eliminate the y term, multiply the first equation by 2 and add the second equation.
6x-4y = 2
-6x + 4y = -2


Adding the equations together you get 0=0 which is always true.  This means that they are indeed the same line, and the solution is the entire line.


R^2 at SCC