Find a. b if a = 9i - 6j, b = 5i + 5

Solution:

Given, a = 9i - 6j, b = 5i + 5j

We have to find a.b

If the two vectors are expressed in terms of unit vectors, i, j, k, along the x, y, z axes, then the scalar product is given by

a.b = a₁b₁ + a₂b₂ + a₃b₃

Here, a₁ = 9, a₂ = -6, b₁ = 5 and b₂ = 5

a.b = (9i - 6j).(5i + 5j)

= 9(5) + (-6)(5)

= 45 - 30

= 15

Therefore, a.b = 15

Find a. b if a = 9i - 6j, b = 5i + 5

Summary:

If a = 9i - 6j, b = 5i + 5j, then a.b is 15.