Question

Solve the system by substitution or elimination.
4x – 6y = –1
8x + 3y = 3

Answer 1

Let's do this one together. Ready?

Answer 2

Would you like to cancel out the x's first or the y's first?

Answer 3

X'S FIRST

Answer 4

Awesome. So we have 4x and 8x to work with. Your best bet is to change the 4x into -8x. What would we multiply 4x by to get -8x?

Answer 5

Also, let me know if it makes sense why we're trying to get -8x. If you don't understand, please tell me and I'll explain.

Answer 6

EXPLAIN MORE PLEASE KINDA CONFUSED

Answer 7

Sure thing!

So you see that our original equations were

4x – 6y = –1
8x + 3y = 3

Answer 8

Now, if we were to add them together like they are right now, we'd have
12x -3y = 2

However, we want to multiply one of the equations by something that would give us 0x.

Answer 9

OK

Answer 10

So, if we keep our
8x + 3y = 3 just the way it is, we'd want equation 2 to say -8x somewhere.

That way, you'd have 8x - 8x + (blah blah) = blah blah.

The 8x and the -8x would kill the x's completely so that all we have to work with is y.

So, what do we multiply the equation,
4x – 6y = –1
by to get -8x in the front?

Answer 11

yes I understand that now, now what about the other part?

Answer 12

Well, tell me what number we'll multiply by so that we can do the next step.

Answer 13

would it be the 3?

Answer 14

If you multiply by 3, you'd get this:
3(4x – 6y = –1)
8x + 3y = 3
Which would turn into
12x -18y = -3
8x + 3y = 3

And adding the x's would give you 20x, not 0x.

Remember, you want to multiply the 4x by something to give you -8x, so that when you add the -8x to 8x, you get 0x. So what do we multiply 4x by to get 8-x?

Answer 15

I meant "...4x by to get -8x?"

Answer 16

3?