Linear System with Two Variables

[Atomised]

Homework Statement

Solve:

(A) 1.7x + 2.3y = 3.5

(B) 2.8x + 3.2y = -9.5

Homework Equations

Without using quadratic formula.

The Attempt at a Solution

I hate to admit it but I am having trouble with this. Seems to lead to monstrous calculations.

I tried subtracting B/4 from A to get x + 3.1 y = 5.875.

Also, substituting letters for numbers.

Is there something I'm missing or is this just a very tedious calculation?

 

[Ray Vickson]

Homework Statement

Solve:

(A) 1.7x + 2.3y = 3.5

(B) 2.8x + 3.2y = -9.5

Homework Equations

Without using quadratic formula.

The Attempt at a Solution

I hate to admit it but I am having trouble with this. Seems to lead to monstrous calculations.

I tried subtracting B/4 from A to get x + 3.1 y = 5.875.

Also, substituting letters for numbers.

Is there something I'm missing or is this just a very tedious calculation?

You have made a start; now just keep going. You have x = 5.875 - 3.1 y, so now wherever you see x you can substitute in that above expression. That will give you an equation involving y alone. That will then be easy to solve. OK: it is messy and takes time, but welcome to equation solving.

 

[Atomised]

Thanks - I realize I made a stupid mistake which unnecessarily complicated things.

 

[SteamKing]

Why would you think the quadratic formula would be used in solving simultaneous equations?

 

[Atomised]

My cack-handed manipulations resulted in x's on LHS and reciprocal y's on RHS. Thanks for your all help - it is a tremendous resource.

 

[HallsofIvy]

By the way, where did you get the word "Dysfunction"? Is that a translation from another language?

 

[Atomised]

Just means pathological. Greek in origin. I have proven that the problem I am currently working on is non-understandable at x_n, for all n.

 

[Mark44]

It's not really a complicated problem ("monstrous calculations" is really hyperbole). It's just a system of two linear equations, which is about the simplest possible system you could be given. Each of the equations represents a line, and the solution of the system is the point at which the lines intersect. A very cursory inspection of the two equations is enough to say that there is a unique solution to the system.

 

[Atomised]

Easy in principle. I was frustrated by my apparent inability to juggle six figure decimals (even with HP42S to help, me the world's best calculator). I have proven that the problem I am currently working on is non-understandable at x_n, for all n.

 

[Mark44]

Easy in principle. I was frustrated by my apparent inability to juggle six figure decimals (even with HP42S to help, me the world's best calculator).


I have proven that the problem I am currently working on is non-understandable at x_n, for all n.

You have proven that you write things that you don't understand...

 

[Mentallic]

What does "non-understandable" mean? You may want to post the entire problem, because your proof already sounds a little misconstrued.

 

[Mark44]

What does "non-understandable" mean? You may want to post the entire problem, because your proof already sounds a little misconstrued.

It's not a proof - the exercise is just to find the solution of a system of two linear equations.

The "non-understandable" bit is just the OP being dramatic, IMO.

 

[Atomised]

The 'non-understandable' was just the supposedly witty signature comment set on my PF app. Now removed.