SOLUTION: 1.true or false: -3x-6y=-21 9x+6y=-9 2.which is addition method and substitution method? x=7y+14 2x+15y=-75 4x-7y=14 2x+15y=-75 thank you so much

Question 63942: 1.true or false:
-3x-6y=-21
9x+6y=-9

2.which is addition method and substitution method?
x=7y+14
2x+15y=-75
4x-7y=14
2x+15y=-75
thank you so much
Answer by tutorcecilia(2152) (Show Source): You can put this solution on YOUR website!
1.true or false:
-3x-6y=-21
9x+6y=-9
___________ [Subtract the equations]
6x=-30
x=-5 [Substitute and solve for y]
.

-3(-5)-6y=-21
15-6y=-21
-6y=-21-15
-6y=-36
y=6
.
checking:
9(-5)+6(6)=-9
-45+36 =-9
-9=-9, so the answer is true, x=-5 and y=6 for both equations.

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