Question

How would you solve system of equation using
mulitplication?
8y-7y= -1

7y-3y=2

Answer 1

Hm, using multiplication...? I would solve this using row reduction. Also, did you mean 8y - 7y = -1 and 7y - 3y = 2, or was there a second variable used?

Answer 2

Um, are there just all y's involved here or x's and y's?

Answer 3

ahh! there are x's
the first two are x on both; 8x and 7 x

Answer 4

Ok. Are you using matrices to solve problems like this in class?

Answer 5

no actually, I am learning from Khan academy but I am really confused. Supposedly there is 3 methods, subsitution multiplication and graphing..

Answer 6

I need help on mulitplication

Answer 7

Ok. Well, here is what I would do. Multiply the top equation by 7 and the bottom one by 8. That should make the coefficients of x the same (56). Then you can subtract the bottom equation from the top one to get some number times y = another number. You can solve for y from there.

Answer 8

multiplication is the same as elimination as we have to multiply the equations by suitable numbers..

Answer 9

Would you do that, plug it back into the top equation, and do the same thing for x?

Answer 10

Once you have y, you can either do the same kind of thing to get x or you can substitute your y value back in to either equation. I'm not sure if you're supposed to substitute back in though, so try doing the multiplication thing again for x.

Answer 11

(So you'd multiply the top one by 3 and the bottom by 7. Basically, multiply by the other equation's coefficient for the variable you want to get rid of.)

Answer 12

Thank you both!! Another problem is sometimes I end up with a fraction for the y variable?

Answer 13

That's ok, no worries. You can have fractions for your answers. Solving a system of equations like this is basically asking "What numbers can I use for x and y that will make both of these equations true?" So it's totally legit if they're fractions.