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In this problem, we will consider this system of simultaneous equations:
3x+5y6z=2,(i)5xy10yz6xz=41,(ii)xyz=6.(iii)

Let a=3x, b=5y, and c=-6z.

 

Given that (x,y,z) is a solution to the original system of equations, determine all distinct possible values of x+y.
 

 Mar 5, 2022
 #2
avatar+118714 
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I have forgotten how to do this.  crying

 

I would like to be reminded of the method though.  Any takers?

 Mar 6, 2022
 #3
avatar+33660 
+2

Here's one way (messy though!):

 Mar 6, 2022
 #4
avatar+67 
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What would the other options be exactly?

shananigans  Mar 6, 2022
 #5
avatar+118714 
+2

Thanks very much Alan,

I finally managed it with a different method.

 

3x+5y6z=2,(i)5xy10yz6xz=41,(ii)xyz=6.(iii)

 

Let 

a=3xx=a3b=5yy=b5c=6zz=c6

 

The above equations become 

a+b+c=2ab+bc+ac=123abc=540

 

This gave me a hint:

If a,b and c are the roos of a monic cubic equations then we have.

 

Note: I used g because x has a different meaning in this question.

 

g3(a+b+c)g2+(ab+bc+ac)g(abcd)=0g3(2)g2+(123)g(540)=0g32g2123g+540=0

I used the wolfram|alpha calculator to factoize this and got

 

(g9)(g5)(g+12)=0

 

so        a,b,c = -12,5,9     (any order)

These can be arranged in 3! = 6 ways so there will be 6 answers.

 

To show all the possible answers I made up a Excel table:

 

 

Alan thinks that there are 9 solutions but i don't know what the others could be ....

Notice that my last solution is the one that Alan found.  

 Mar 7, 2022
 #6
avatar+33660 
+2

Nicely done Melody.  Here are the answers found by Mathcad (I should have said 6, not 9):

Alan  Mar 7, 2022
 #7
avatar+118714 
0

Thanks Alan  laugh

Melody  Mar 7, 2022

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