x+y=-10

7x-5y-6z=200

12x+6y+z=-35   
how do you solve the problem
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1 Answer

Since x+y=-10, y=-10-x, so we can substitute for y in the other equations:

7x-5(-10-x)-6z=200, 7x+50+5x-6z=200, 12x-6z=150, 2x-z=25.

12x+6(-10-x)+z=-35, 12x-60-6x+z=-35, 6x+z=25.

Now we have two equations and two unknowns:

2x-z=25

6x+z=25

Add them together:

8x=50, x=50/8=25/4. 2x=25/2, so z=2x-25=25/2-25=-25/2.

And y=-10-x=-10-25/4=-(10+25/4)=-65/4.

SOLUTION: x=25/4, y=-65/4, z=-25/2.

by Top Rated User (677k points)

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