Question

Select the best possible first step to solving the system by first eliminating the x variable.

x - 3y = 12
2x + 5y = 2

Multiply the first equation by 2.
Multiply the second equation by 2.
Multiply the first equation by -2.
Multiply the second equation by -2.

Doesn't a and c work?

Answer 1

@amistre64

Answer 2

can you help me?

Answer 3

multiply the 1st eq by 2

Answer 4

2x-6y=24
2x+5y=2 then you add them

Answer 5

i would say A

Answer 6

if you multiply it by 2 then subtract them
if you multiply it by -2 then add them up.

Answer 7

yes but that's were I was confused.

Answer 8

both eliminate x in a different way

Answer 9

right :/

Answer 10

yes...

Answer 11

True. But multiplying by -2 and adding is a bit simpler than subtracting.

Answer 12

but i can't do 2 answers

Answer 13

yuuuppp...but use which you think is easeir...

Answer 14

ok thx

Answer 15

@yungrichneegu @radar what do you think?

Answer 16

@mathmate

Answer 17

I would multiply the first equation by -2 and then add them....that will eliminate the x's
but your right...you could multiply the first equation by 2, and then subtract them. Either way will work.

Answer 18

Alright, thanks! so if I pick either one its right?

Answer 19

I, myself, think the adding is simplier...but you can choose either way.

x - 3y = 12 --->(-2)
2x + 5y = 2
---------------
-2x + 6y = -24 (result of multiplying by -2)
2x + 5y = 2
---------------add
11y = - 22
y = -2

or
x - 3y = 12 --->(2)
2x + 5y = 2
-------------
2x - 6y = 24
-(2x + 5y = 2)
-------------
now just distribute the negative through the parenthesis
so now we have
2x - 6y = 24
-2x - 5y = -2
---------------
-11y = 22
y = -2

Answer 20

okay!

Answer 21

Personally, I suggest multiplying by a positive number and decide later to add or subtract. This will avoid multiplying by a negative number and get lost with the sign.
But this is a subjective opinion. Everyone has a different favourite procedure.