- #1
nobahar
- 497
- 2
Hello!
How do I determine if there is a solution to the following simultaneous equation?:
2a+3b=7
5a+7b=19
9a+5b=32
I have given a specific example but I was interested in the general case. I am confused because I have seen examples with two equations and two unkowns where it has been argued that, if, for example, I have:
2a+4b=x1
5a+6b=x2
Then:
[tex]a=\frac{1}{2}(x_{2}-\frac{3}{2}x_{1})[/tex]
[tex]b=\frac{1}{4}({\frac{5}{2}x_{1}-x_{2})[/tex]
and I can plug in any x1 and any x2 and get an answer, as there is no division by zero, etc, and so there is no reason why I can't get an output for a and c.
I can represent my original three equations in a similar format; presenting a as a combination of the outputs and b as a combination of the outputs. But when I put them into the original equation it doesn't work!
Has this something to do with an assumption being made? That with two equations and two unknowns, I can always find a solution for any x1 and x2 (provided that they're not parallel), but for three equations and two unknowns, there is not always going to be a solution? If this is the case, how do I ascertain that there is not a solution (without graphing the functions)?
As always, any help appreciated.
How do I determine if there is a solution to the following simultaneous equation?:
2a+3b=7
5a+7b=19
9a+5b=32
I have given a specific example but I was interested in the general case. I am confused because I have seen examples with two equations and two unkowns where it has been argued that, if, for example, I have:
2a+4b=x1
5a+6b=x2
Then:
[tex]a=\frac{1}{2}(x_{2}-\frac{3}{2}x_{1})[/tex]
[tex]b=\frac{1}{4}({\frac{5}{2}x_{1}-x_{2})[/tex]
and I can plug in any x1 and any x2 and get an answer, as there is no division by zero, etc, and so there is no reason why I can't get an output for a and c.
I can represent my original three equations in a similar format; presenting a as a combination of the outputs and b as a combination of the outputs. But when I put them into the original equation it doesn't work!
Has this something to do with an assumption being made? That with two equations and two unknowns, I can always find a solution for any x1 and x2 (provided that they're not parallel), but for three equations and two unknowns, there is not always going to be a solution? If this is the case, how do I ascertain that there is not a solution (without graphing the functions)?
As always, any help appreciated.