HOW SHOULD I DO THIS PROBLEM?????

x + y = k
2x + 3y = k + 1
The point of intersection of the lines has an x-coordinate of

2k + 1
-2k + 1
2k - 1

Question

HOW SHOULD I DO THIS PROBLEM????? 

x + y = k
2x + 3y = k + 1
The point of intersection of the lines has an x-coordinate of


2k + 1
-2k + 1
2k - 1

anonymous · Answer

multiply the top equation by -3 to eliminate the y's giving you

-3x - 3y = -3k
 2x + 3y =    k + 1

-x + 0y = -2k + 1

-x = -2k + 1

x = 2k - 1

anonymous · Answer

thankx

anonymous · Answer

hey, how did u come up with -3????

anonymous · Answer

because you are only wanting the x coordinate so you have to make y go away. And the only way to do that is to multiply the top equation by -3 so when you add the two equations together your x's are still there but you get a 0*y and zero times anything is 0 so the y's cancel which is what you want.

anonymous · Answer

ok thankx for the help

anonymous · Answer

how about this one????

Solve the system by the elimination method. 
2x + y - 4 = 0
2x - y - 4 = 0 
When you eliminate y, what is the resulting equation?


x = 0
4x = -8
4x = 8