Math Is Fun Forum

Don Ventresca

Member

Registered: 2008-12-17

Posts: 1

3x+5y=15

Yes, a relatively simple problem (as said by my math teacher) but I can't figure out the formula/our teacher thought we would know this from 7th grade. (which I don't)

If someone could explain the formula for this sort of problem, it would greatly be appreciated.

Oh and I'm new here.

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,045

Re: 3x+5y=15

Hi Don Ventresca,

3x+5y=15
This is an equation in two variables (x and y) of degree 1.
For solving two variables, minimum of two equations are required.
These are called simultaneous equations.

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Don Ventresca

Member

Registered: 2008-12-17

Posts: 1

Re: 3x+5y=15

So, subtract 3x from both sides to solve for x? 5y=15-3y?

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Re: 3x+5y=15

This has an infinite number of solutions i.e. every point on the line y = -3/5x + 3.

Does the question specify that x and y are integers? (this still has an infinite number of solutions and all of them lie on that line, but at least it actually gives some work to do).

Last edited by Daniel123 (2008-12-17 03:42:25)

Don Ventresca

Member

Registered: 2008-12-17

Posts: 1

Re: 3x+5y=15

No, x & y are a undefined number, thanks to you Daniel, I may not fail my math test tomorrow. But don't you need to divide out the 3?

Last edited by Don Ventresca (2008-12-17 04:14:37)

careless25

Real Member

Registered: 2008-07-24

Posts: 560

Re: 3x+5y=15

Don he doesnt need to divide out the three.

Daniel did this:

Last edited by careless25 (2008-12-17 11:34:47)