1) 3(a-b)=9

2) 4a=b+2

How do I acheive an ordered pair via the elimination method with this equation?? (Punch)

Thanks much!

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- May 20th 2011, 07:53 PMjay1Elimination method
1) 3(a-b)=9

2) 4a=b+2

How do I acheive an ordered pair via the elimination method with this equation?? (Punch)

Thanks much! - May 20th 2011, 08:04 PMjohnny
1. a - b = 3, i.e. b = a - 3.

2. b = 4a - 2

a - 3 = 4a - 2, i.e. -3 + 2 = 4a - a.

4a - a = 3a and -3 + 2 = -1, i.e. 3a = -1, hence a = -1/3 and b = -1/3 - 3 = -10/3.

∴ (a, b) = (-1/3, -10/3) - May 22nd 2011, 06:18 AMDrSteve
Johnny did NOT use the elimination method - he used substitution:

3(a-b)=9

4a=b+2

a - b = 3

4a - b = 2

I'm going to multiply the first equation by -1, then add the two equations:

-a + b = -3

4a - b = 2

3a = -1

a = -1/3

Now substitute a into either equation to find b.