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


Sagot :

[tex] \left \{ {2x + 4y =12} \atop {3x + y = 9}} \right. [/tex]

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 =) 
View image Bellalesse