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1. hi there, ive been stuck on this bit of vector product proof kind of thing for quite a while, need a bit of help thanks

x1a1+x2a2+x3a3=0

x1b1+x2b2+x3b3=0

how do i eliminate x3?

i cant seem to find a way

btw x1 means x with a little 1, showing theres 3 different x's, same with a's and b's
2. put the x3 on its own in both cases and then equate the two different equations!
3. (Original post by chr15chr15)
put the x3 on its own in both cases and then equate the two different equations!
Yes!
4. To write you can use latex. See here:How to use LaTeX
5. In general, you solve simultaneous equations by eliminating the variables one at a time.

In this case, you pick an equation with the variable you want to eliminate in it (either will do), multiply / divide by some constant so the co-efficient of that variable is 1 (in the first; divide through by giving . Now, you subtract from to every other equation you have, some multiple of this equation, chosen so that it cancels the variable you're eliminating.
Spoiler:
Show
So for this we'd subtract lots of the (modified) first equation from the second, giving
6. (Original post by pyrolol)
In general, you solve simultaneous equations by eliminating the variables one at a time.

In this case, you pick an equation with the variable you want to eliminate in it (either will do), multiply / divide by some constant so the co-efficient of that variable is 1 (in the first; divide through by giving . Now, you subtract from to every other equation you have, some multiple of this equation, chosen so that it cancels the variable you're eliminating.
Spoiler:
Show
So for this we'd subtract lots of the (modified) first equation from the second, giving
but you won't be able to solve this system of equations with only 2 equations.
7. god how did i not think of that cheers

and thanks for the latex thing Simon
8. (Original post by Totally Tom)
but you won't be able to solve this system of equations with only 2 equations.
Course not, that first line was more a vague mention.

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