Respuesta :

absor201

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

kudzordzifrancis

ANSWER

[tex]a \cdot \: b = - 4[/tex]

EXPLANATION

The dot product of two vectors

[tex]a = xi + yj[/tex]

and

[tex]b = mi + nj[/tex]

is given by

[tex]a \cdot \: b = mx + ny[/tex]

The given vectors are:

[tex]a = 4i - 4j[/tex]

[tex]b = 4i + 5j[/tex]

Applying the above definition of dot products, we obtain:

[tex]a \cdot \: b = 4 \times 4 + - 4 \times 5[/tex]

[tex]a \cdot \: b = 16 - 20[/tex]

[tex]a \cdot \: b = - 4[/tex]

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