Question

Evaluate the dot product of (7,5)and (-5,4)

Answer 1

`(7i+5j)\cdot(-5i+4j)=-15`

Explanation:

The given two points are:

`(7,5) and (-5,4)`

Writing them in vector form, we get

`(7i+5j) and (-5i+4j)`

Now, the product of these two vectors is given as:

=
`(7i+5j)\cdot(-5i+4j)`

=
`(-5)(7)+(5)(4)`

=
`-35+20`

=
`-15`

Therefore,
`(7i+5j)\cdot(-5i+4j)=-15`

which is the required dot product.

Answer 2

To evaluate the dot product of (7,5) and (-5,4)
this can be written in vector form as:
7i+5j and -5j+4j
thus the dot product will be:
(7i+5j)*(-5j+4j)
=(-5*7)+(5*4)
=-35+20
=-15
thus the answer is -15