Can anyone help me with this problem:

http://img819.imageshack.us/img819/2552/imgpv.jpg

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- Feb 11th 2011, 05:26 PMziane0210Vectors
Can anyone help me with this problem:

http://img819.imageshack.us/img819/2552/imgpv.jpg - Feb 11th 2011, 05:28 PMAckbeet
This is more of a pre-calc or algebra question, just fyi. You can report your own post (use the little triangle symbol with the exclamation mark in it), and a mod will move it for you.

What ideas have you had so far? - Feb 11th 2011, 06:46 PMProve It
(ii) Try evaluating the dot product...

- Feb 12th 2011, 04:13 AMHallsofIvy
Any vector that is parallel to $\displaystyle \vec{i}+ 2\vec{j}$ is of the form $\displaystyle a\vec{i}+ 2a\vec{j}$. Any vector that is perpendicular to $\displaystyle 3\vec{i}+ \vec{j}$ is of the form $\displaystyle b\vec{i}- 3b\vec{j}$. Find a and b so that $\displaystyle a\vec{i}+ 2a\vec{j}+ b\vec{i}- 3b\vec{j}= \vec{i}+ \vec{j}$