Originally Posted by
keaton Thanks for the help.
i used a+λb
then written in terms of i and j gives:
(1-3λ)i + (λ-2)j=-i-3j No!. Those vectors are not equal, they are parallel, which means that they are scalar multiples of each other. Look at the previous comments to see how to deal with that.
so
(i)=-1 Please don't write anything like this in your A-level paper!
(j)=-3 i and j are unit vectors in the directions of the coordinate axes. They are not numbers, and it makes no sense to put them equal to –1 or –3.
to make them the same *(i) by 3 giving: (and if a is parallel to be a=b)
3(1-3λ)=(λ-2)
which symplifies to get:
3-9λ=λ-2
so λ=1/2 However, you have got the right answer, so maybe there is something in this method. But it doesn't look good to me.