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My teacher provided me with a practice test for an upcoming exam, and he is not

ID: 3100111 • Letter: M

Question

My teacher provided me with a practice test for an upcoming exam, and he is not going to provide us with the answers to it. I did most of the practice test, but I want to be sure I did them right.

My answers:

15) D

16) B

17) C

18) D

15)
x+y=-6
x+y=-9

a) x=0, y=0; (0,0) b) x=0, y=-15; (0,-15) c) x=-6, y=-9; (-6,-9) d) inconsistent

16)
x+5y=-3
3x+15y=-9

a) x=0, y=0; (0,0)
b) x=-3, y=0; (-3,0)
c) y= (-x/5)- (3/5) where x is any real number or (x,y) is y= -(x/5)-(3/5) where x is any real number
d) inconsistent

17)

x-y+3z=-2
3x + z=0
x+4y+z=8

a) x=0, y=2, z=-2; (0,2,-2)
b) x=0, y=0, z=2;(0,0,2)
c) x=0, y=2, z=0; (0,2,0)
d) inconsistent

18)

x+y+z=5
x-y+2z=12
2x+2y+2z=9

a) x=3, y=4, z=-2; (3,4,-2)
b) x=4, y=-2, z=3; (4,-2,3)
c) x=3, y=-2, z=4; (3,-2,4)
d) inconsistent


Explanation / Answer

All of your answers are correct!