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Solving equations with three unknowns

Hi,

Could someone please help me with solving equations for three unknowns:

A) 2x + 2y - 5z = -5
x - y + z = 3
-3x + y + 2z = -2

B) 3x + 2y - 2z = -5
4x + 3y + 3z = 17
2x - y +z = -1

Literally dont even know where to start, other than I assume you would have to get 1 term the same in 2of the equations?

Thanks
Hi,

For A) Try use middle equation to eliminate z from the other two equations. So for example:

2x + 2y - 5z = -5 (1)
x - y + z = 3 (2)
-3x + y + 2z = -2 (3)

Do (1) + 5 times (2), and (3) - 2 times (2), you should then get two equations in x and y.

Have a go, you will see.
Original post by matt_brown67
Hi,

Could someone please help me with solving equations for three unknowns:

A) 2x + 2y - 5z = -5
x - y + z = 3
-3x + y + 2z = -2

B) 3x + 2y - 2z = -5
4x + 3y + 3z = 17
2x - y +z = -1

Literally dont even know where to start, other than I assume you would have to get 1 term the same in 2of the equations?

Thanks

Rearrange one of the three equations for one of the variables. Then substitute it into the other two equations. You should now have two equations in terms of two variables (the two that you did not choose to rearrange for with one of the equations).

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