Elimination Problems

[susieq00]

I worked out these two problems and i got -3 for both equations. Is that right ?

1. You want get rid of the x by elimination in the system below.
3x+4y=7
4x-2y=24

If you multply the top equation by 4, by which number will you multply the bottom equation?

2. You want to get rid of the y by elimination in the system below.

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

If you multiply the top equation by 6, by which number will you multiply the bottom equation ?

 

[stapel]

I'm sorry, but I don't understand your question. You ask if it's "right" that you "got -3 for both equations". What does this mean? You're supposed to be finding values for the variables, not for the equations...?

1) You ask what one would multiply against the second equation, given that you have already multipled "4" against the first equation and that you're trying to eliminate the x-variable values.

What do you get for the x-variable term in the first equation? What would you need in the second equation for this term to cancel out? So what would you need to multiply on the "4x" to get this value?

2) See my comments on (1).

Eliz.

 

[Unco]

G'day, Susie.

1. Correct, if we are going to add the two resulting equations.

2. They are wanting to eliminate y (not x), albeit by multiplying by a larger number than necessary.

Multiplying the top equation by 6 gives
6x - 12y = -6

So what must you multiply the bottom equation
2x - 3y = 4
by to eliminate the y term by adding the two equations? (How about by subtracting?)

 

[Denis]

I worked out these two problems and i got -3 for both equations. Is that right ?

Just like Stapel, may I inquire: WHAT THE **** IS -3 ?!

1. You want get rid of the x by elimination in the system below.
3x+4y=7
4x-2y=24
If you multply the top equation by 4, by which number will you multply the bottom equation?

WHY multiply top by 4? Why not simply multiply bottom by 2 and be finished?

2. You want to get rid of the y by elimination in the system below.
x-2y=-1
2x-3y=4
If you multiply the top equation by 6, by which number will you multiply the bottom equation ?

WHY multiply top by 6? Why not simply multiply it by 2 and be finished?

 

[stapel]

WHY multiply top by 6? Why not simply multiply it by 2 and be finished?

I would guess that the text is trying to spoon-feed this student. But until she follows the instructions and looks at what is going on, I'm afraid not much progress is going to be made.

Eliz.