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malfutka [58]
3 years ago
7

Find a ⋅ b. a = 4i - 4j, b = 4i + 5j

Mathematics
2 answers:
Alchen [17]3 years ago
8 0

ANSWER

a \cdot \: b =  - 4

EXPLANATION

The dot product of two vectors

a = xi + yj

and

b = mi + nj

is given by

a \cdot \: b = mx + ny

The given vectors are:

a = 4i - 4j

b = 4i + 5j

Applying the above definition of dot products, we obtain:

a \cdot \: b = 4 \times 4 +  - 4 \times 5

a \cdot \: b = 16   - 20

a \cdot \: b =  - 4

svetoff [14.1K]3 years ago
7 0

Answer:

value of a.b = -4

Step-by-step explanation:

We need to find a.b

a= 4i-4j

b = 4i+5j

We know that i.i =1, j.j=1, i.j =0 and j.i=0

a.b = (4i-4j).(4i+5j)

a.b = 4i(4i+5j)-4j(4i+5j)

a.b = 16i.i +20i.j-16j.i-20j.j

a.b = 16(1) +20(0)-16(0)-20(1)

a.b = 16 +0-0-20

a.b = 16-20

a.b =-4

So, value of a.b = -4

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