Question

Find a ⋅ b. a = 9i - 6j, b = 5i + 5j

Answer 1

Hello!

The answer is: $a.b=15$

Why?

It's a scalar product of vectors. The scalar product gives as result a or scalar number.

The scalar product consists in multiplying the axis components each other (x-component by x-component and so) and them performing an algebraic sum.

So, the scalar product of the given vectors will be:

$a.b=ax*bx+ay*by=9*5+(-6*5)=45-30=15$

Have a nice day!

Answer 2

(9i - 6j)(5i + 5j)
Use FOIL:
45i^2 + 45ij - 30ij -30j^2
Combine like terms:
45i^2 - 30j^2 + 15ij