Math CentralQuandaries & Queries


Question from Tiffany, a student:


x + y + z = 4
2x - 3y - z = 1
4x + y - 2z = 16


Hi Tiffany,

What I see first is z in the first equation and -z in the second equation so if I add the equations the z terms will cancel. Thus add equation 1 to equation 2 to get

3x - 2y = 5

To obtain another equation with z eliminated multiply the first equation by 2 and add the result to the third equation. This gives

6x + 3y = 24

Can you now solve these two equations for y?


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