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Solution:
Given, a = 4i + 8j, b = -2i + 3j
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 = 4, a₂ = -2, b₁ = 8 and b₂ = 3
a.b = (4i + 8j).(-2i + 3j)
= 4(-2) + 8(3)
= -8 + 24
= 16
Therefore, a.b = 16
Summary:
If a = 4i + 8j, b = -2i + 3j, then a.b is 16.