# What is the answer on 2x+4y=12 3x+y=9 using elimination method

1
by Draco

2015-10-09T00:20:39+08:00

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Think of a number that if you multiply it by the equation would eliminate one variable.

So in this case, I'll use the equation:

3x + y = 9

What number should be multiplied by the equation above that when you combine it with 2x + 4 = 12 would eliminate one variable?

2x + 4y =12
(3x + y = 9) -4 ⇒ -12x - 4y = -36

2x + 4y = 12
-12x - 4y = -36
-----------------------
-10x = -24

-10x    -24               24                                12
------- = -----  ⇒   x = ----- (lowest term) ⇒ x =  ----
-10      -10               10                                 5

(Now substitute to find y)

2x + 4y = 12

2(12/5) + 4y = 12

24/5 + 4y = 12

I want to remove the fraction part so I'll find for their lcd

(24/5 + 4y = 12) 5

24 + 20y = 60

20y     36           36              9
-----  = ---- ⇒ y = -----  ⇒ y = -----
20       20           20              5

CHECK:

3x + y = 9

3(12/5) + 9/5 = 9

36/5 + 9/5 = 9

45/5 = 9

9 = 9

Check the attachment below =)
Lovely :-) The only link missing is the graph. Everyone, rest your case. This is how this problem is solved. How can I vote 5-star? :-) :-) :-)
Omg really??? HAHA thank you so much po :)))