# Thread: I need proof...

1. ## I need proof...

I need proof for the problem:
What are the values of x and y?
50x+100y=900
x+1.5y=15.5

The answer is x=8 and 5=y. I simply guessed and my teacher requires proof.
The proof cannot be a guess and check method.

2. Originally Posted by ceasar_19134 I need proof for the problem:
What are the values of x and y?
50x+100y=900
x+1.5y=15.5

The answer is x=8 and 5=y. I simply guessed and my teacher requires proof.
That is proof!
If it works that is your proof.

3. Originally Posted by ceasar_19134 I need proof for the problem:
What are the values of x and y?
50x+100y=900
x+1.5y=15.5

The answer is x=8 and 5=y. I simply guessed and my teacher requires proof.
The proof cannot be a guess and check method.
Multiply the second equation by 50 to get the pair of equations:

50x+100y=900
50x+75y=775

Now subtract to get:

25y=125.

And I expect you can take it from there.

RonL

4. Originally Posted by ThePerfectHacker That is proof!
If it works that is your proof.
Sounds like a rather "Physics-y" proof if you ask me. -Dan

5. Originally Posted by topsquark Sounds like a rather "Physics-y" proof if you ask me. -Dan
Why?

The reason why you use a technique or method to solve a problem is because you do not want to guess through uncountably many possibilities

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