Find the resultant of vectors `veca=hati-hatj+2hatk and vecb=hati+2hatj-4hatk`. Find the unit vector in the direction of the resultant vector.

Explanation

To solve the problem, we will follow these steps:

### Step 1: Write down the vectors
Given vectors are:
\[ \vec{a} = \hat{i} - \hat{j} + 2\hat{k} \]
\[
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