Simultaneous equation

Monkeyseat

Full Member
Joined
Jul 3, 2005
Messages
298
Hi,

I don't know what I'm doing wrong here, I've tried this several times and I'm apparently getting the wrong answer.

This is the equation:



I got y = -2 and x = 2. The book says the answer is x = 2 1/2 and y = -1 3/4.

Why do my answers work in this equation? I've tried numerous methods and keep coming up with the same answers. Here's what I did:



I've tried other methods like eliminating y and I still get the same. I also tried re-arranging it differently. If you can stick to elimination.

Please help and tell me where I am going wrong ASAP (need to know for tomorrow if you can). Maybe it was the re-arranging? I just multiplied the bottom of the fraction on both sides.

Excuse the handwriting. :p

Thank you very much. :)
 

rahidz2003

New member
Joined
Oct 1, 2005
Messages
25
Quite frankly, I think you're right :p

If x = 2.5 and y = -1.75, then the second equation becomes

(2.5-7)/(2*-1.75+3)=
(-4.5)/(-3.5+3)=9

So I'm guessing the book's wrong.
 

Monkeyseat

Full Member
Joined
Jul 3, 2005
Messages
298
Thanks for the reply.

Odd, when I checked it with their answer before I got 5 lol. Have I re-arranged them correctly? I've tried a few other ways like eliminating y and always get the same.

The book is sometimes wrong but so am I so I just want to check if anyone did get a different answer.

Many thanks. :)
 

Subhotosh Khan

Super Moderator
Staff member
Joined
Jun 18, 2007
Messages
18,190
Monkeyseat said:
Hi,

I don't know what I'm doing wrong here, I've tried this several times and I'm apparently getting the wrong answer.

This is the equation:



I got y = -2 and x = 2. The book says the answer is x = 2 1/2 and y = -1 3/4.

Why do my answers work in this equation? I've tried numerous methods and keep coming up with the same answers. Here's what I did:



I've tried other methods like eliminating y and I still get the same. I also tried re-arranging it differently. If you can stick to elimination.

Please help and tell me where I am going wrong ASAP (need to know for tomorrow if you can). Maybe it was the re-arranging? I just multiplied the bottom of the fraction on both sides.

Excuse the handwriting. :p

Thank you very much. :)
You checked -- excellent and you are correct.

Book's answers are wrong - if you use those you'll see that those do not check with the original equations.
 

Monkeyseat

Full Member
Joined
Jul 3, 2005
Messages
298
Yeah they both seem to be wrong with their answers. I must have just made a typo when checking them (well I think on the first). My answers are right from the original equation aren't they not just the re-arranged bit (which did I also do the correct technique?)? I know you said it's right but I was just wondering about that.

Still thank you very much for clarifying. I did check with my answers if that's what you mean but it's really annoying when the books make mistakes which I've seen countless times. :x Doesn't help when I mess up checking their answers lol. XD I don't even know how the heck they got that answer. Much appreciated.

By the way Subhotosh Khan I have not forgotten about the HCF/LCM thread, I have just been very busy and not had any time to get around to it (it wasn't work just something I was wondering about) so I do apologise but I will sort it out soon, maybe in a couple of days. Just so busy. If you have clarified again it's much appreciated.

Thank you both. :)
 
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