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3X - 4Y = 9

-3X + 2Y = 9

 May 29, 2014

Best Answer 

 #1
avatar+129852 
+5

Notice that, if we add the equations, we can "eliminate" X....so we have

      3X - 4Y = 9

+ (-3X + 2Y = 9)    This gives us

           -2Y = 18     divide by -2 on both sides

              Y = -9

To find X, just substitute for Y in one of the equations....I'll use the first one

3X - 4(-9) = 9

3X + 36 = 9        Subtract 36 from both sides

3X= -27              Divide  by 3 on both sides

X= -9

And here's the solution     ......  (X , Y)  = (-9 ,  -9)

You should check this answer in both equations to verify for yourself.

 May 29, 2014
 #1
avatar+129852 
+5
Best Answer

Notice that, if we add the equations, we can "eliminate" X....so we have

      3X - 4Y = 9

+ (-3X + 2Y = 9)    This gives us

           -2Y = 18     divide by -2 on both sides

              Y = -9

To find X, just substitute for Y in one of the equations....I'll use the first one

3X - 4(-9) = 9

3X + 36 = 9        Subtract 36 from both sides

3X= -27              Divide  by 3 on both sides

X= -9

And here's the solution     ......  (X , Y)  = (-9 ,  -9)

You should check this answer in both equations to verify for yourself.

CPhill May 29, 2014
 #2
avatar+11912 
0

CPhill i cant understand ur answer ! how did u do it ? 

 May 29, 2014

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