HELP! Calling all algebra gurus....

[lovesmurfs]

Okay my DS has been working on this all weekend, and I used to think I knew it, but I'm wondering if this problem on his take-home test has a typo...Or if it's a trick question.

Solve this system by substitution or elimination:

-3x + y = 6
6x - 2y = 25

I solved for y (y=3x + 6), then substitued into the 2nd equation:

6x - 2(3x+6) = 25
6x - 6x - 12 = 25

....and I've just proved that -12 equals 25.

Help!

 

[ajwomic]

Because the slopes are the same, they have to either be the same line or parallel. Since they are not identical, they are parallel. The system of equations is basically finding the intersection of the lines and since the variables "went away" there is no intersection. Hope this helps!
Alicia

 

[lovesmurfs]

Okay my DS has been working on this all weekend, and I used to think I knew it, but I'm wondering if this problem on his take-home test has a typo...Or if it's a trick question.

Solve this system by substitution or elimination:

-3x + y = 6
6x - 2y = 25

I solved for y (y=3x + 6), then substitued into the 2nd equation:

6x - 2(3x+6) = 25
6x - 6x - 12 = 25

....and I've just proved that -12 equals 25.

Help!

I just graphed it out and the lines have the same slope (parallel), so it doesn't look like there's a solution.

 

[redlight]

I think there is a typo because I just proved by elimination that 0 = 37.

 

[taylor3297]

No solution is correct. Former math teacher here.

 

[lovesmurfs]

Because the slopes are the same, they have to either be the same line or parallel. Since they are not identical, they are parallel. The system of equations is basically finding the intersection of the lines and since the variables "went away" there is no intersection. Hope this helps!
Alicia

Thanks! It's been about 30 years since I had algebra!

 

[jcc0621]

DH is a math teacher. When he figured out your problem he came up with 0=37. He said there is something wrong with the problem, but that your DS;s work is correct!

Edited to add: The reason that they dont' share a point of common solution is that they represent parallel lines.

 

[PollyannaMom]

Okay my DS has been working on this all weekend, and I used to think I knew it, but I'm wondering if this problem on his take-home test has a typo...Or if it's a trick question.

Solve this system by substitution or elimination:

-3x + y = 6
6x - 2y = 25

I solved for y (y=3x + 6), then substitued into the 2nd equation:

6x - 2(3x+6) = 25
6x - 6x - 12 = 25

....and I've just proved that -12 equals 25.

Help!

I got the same answer as you.