Question

Help please with vectors

Find | a - b |

a= < -3 , 4 > , b = < 9, -1>

Answer 1

Just to clarify what sillybilly said $$ \| \mathbf a- \mathbf b \| ^2 = (\mathbf a - \mathbf b ) .(\mathbf a - \mathbf b ) $$Therefore $$
\| \mathbf a- \mathbf b \| = \sqrt{ (\mathbf a - \mathbf b ) .(\mathbf a - \mathbf b ) }
$$

Answer 2

The latter can be written more condensely as $$\| \mathbf a- \mathbf b \| = \sqrt{ (\mathbf a - \mathbf b )^2 }$$ with the understanding that multiplication here is scalar dot product

Answer 3

\[\large\rm (a-b) \cdot (a-b)\]
`\cdot`

Answer 4

why did you delete his work ?? -_-