1) The average velocity is 
2) The instantaneous velocity is 
Explanation:
1)
The average velocity of an object is given by

where
d is the displacement
t is the time elapsed
In this problem, the position of the particle is given by the function

where t is the time.
The position of the particle at time t = 6 sec is

While the position at time t = 12 sec is

So, the displacement is

And therefore the average velocity is

2)
The instantaneous velocity of a particle is given by the derivative of the position vector.
The position vector is

By differentiating with respect to t, we find the velocity vector:

Therefore, the instantaaneous velocity at any time t can be found by substituting the value of t in this expression.
Learn more about velocity:
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The way the sound waves hit your eardrums and they are moved by the sound pressure. Then your brain takes over from there.
Taking into account the rule of three for the change of units, the mass of the book is 45600 miligrams.
First of all, the rule of three is a mathematical tool that helps you quickly solve proportionality problems.
Having three known values and one unknown, a proportional relationship is established between all of them in order to find the fourth term of the proportion.
If the relationship between the magnitudes is direct (when one magnitude increases, so does the other; or when one magnitude decreases, so does the other), the rule of three is applied as follows, where a, b and c are known values and x is the unknown to calculate:
a → b
c → x
So: 
Being 1 kg equivalent to 1000000 milligrams, In this case the rule of three is applied as follows: if 1 kg equals 1000000 milligrams, 4.56×10⁻² kg equals how many milligrams?
1 kg → 1000000 milligrams
4.56×10⁻² kg → x
So:

<u><em>x=45600 miligrams</em></u>
In summary, the mass of the book is 45600 miligrams.
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Answer:
Los 0.0416km
esto se debe a que transponemos la fórmula acelerada y obtenemos Distancia = velocidad × tiempo
también recuerda transponer los segundos a horas viendo que la velocidad es por hora
También tenga en cuenta que no hablo español, así que esto fue extremadamente difícil
culto