7x - 3y = 4
2x - 4y = 1

Which of the following system of equations is not equal to the system of equations shown above?

28x - 12y = 16 and -6x + 12y = -3
14x - 6y = 4 and -14x + 28y = 1
-28x + 12y = -16 and 28x - 56y = 14

Question

7x - 3y = 4
2x - 4y = 1

Which of the following system of equations is not equal to the system of equations shown above?

28x - 12y = 16 and -6x + 12y = -3
14x - 6y = 4 and -14x + 28y = 1
-28x + 12y = -16 and 28x - 56y = 14

solomonzelman · Answer

$\color{#000000 }{ \displaystyle 7x - 3y = 4  }$
$\color{#000000 }{ \displaystyle 2x - 4y = 1  }$

I would multiply the first equation times 4,
                  and second equation times -3.

anonymous · Answer

How did you come up with that?

solomonzelman · Answer

I want to make the y-coeffients equivalent, but one of them negative. I want to do this, so that the y goes away when I add the equations.

solomonzelman · Answer

is this reasonable, or are you still confused?

anonymous · Answer

Ohhh

anonymous · Answer

This is very very reasonable... these are new equation..

solomonzelman · Answer

ok, when system of equations do you get when you multiply as I directed?

anonymous · Answer

28x -12y = 16
-6x + 12y = -3

solomonzelman · Answer

$\color{#000000 }{ \displaystyle 28x - 12y = 16  }$
$\color{#000000 }{ \displaystyle -6x +12 y =-3  }$


good!

anonymous · Answer

Oh look! That's the first option!

solomonzelman · Answer

now, add the equations:)

anonymous · Answer

I think I understand it now :D

solomonzelman · Answer

ok, good:)

anonymous · Answer

So...

anonymous · Answer

now let's refer to the question again

anonymous · Answer

7x - 3y = 4
2x - 4y = 1

Which of the following system of equations is not equal to the system of equations shown above?

28x - 12y = 16 and -6x + 12y = -3
14x - 6y = 4 and -14x + 28y = 1
-28x + 12y = -16 and 28x - 56y = 14

anonymous · Answer

It's saying, which is NOT equal

anonymous · Answer

Is it the middle one?

solomonzelman · Answer

well, if you were to attempt to eliminate the x, what would you do with your system?

solomonzelman · Answer

times what number would you multiply equation 1 and equation 2?

anonymous · Answer

I would.... multiply the first equation by 2 and the second by ..

anonymous · Answer

I'm not sure :(

anonymous · Answer

and the second by 7?

solomonzelman · Answer

yes, but, by -7, so that you have 14x in equation 1 and -14x in equation 2 (and addition will cancel them)

anonymous · Answer

OHHH! lol you're a good teacher. What grade are u in?

solomonzelman · Answer

I am in college

anonymous · Answer

That makes sense. I am in grade 10 lol

anonymous · Answer

Thank you !! :D

solomonzelman · Answer

You are welcome!