Determine the factors of x^2 - 8x + 16.
2 answers:
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(a) First find the intersections of 
and 
:
So the area of
is given by
If you're not familiar with the error function
, then you will not be able to find an exact answer. Fortunately, I see this is a question on a calculator based exam, so you can use whatever built-in function you have on your calculator to evaluate the integral. You should get something around 0.5141.
(b) Find the intersections of the line
with .
So the area of
is given by
which is approximately 1.546.
(c) The easiest method for finding the volume of the solid of revolution is via the disk method. Each cross-section of the solid is a circle with radius perpendicular to the x-axis, determined by the vertical distance from the curve and the line , or 
. The area of any such circle is 
times the square of its radius. Since the curve intersects the axis of revolution at 
and 
, the volume would be given by
So the area of
If you're not familiar with the error function
(b) Find the intersections of the line
So the area of
which is approximately 1.546.
(c) The easiest method for finding the volume of the solid of revolution is via the disk method. Each cross-section of the solid is a circle with radius perpendicular to the x-axis, determined by the vertical distance from the curve
All you have to do is plug in the given values into the given equation and evaluate.
The expression is,
But we have to analyze the problem carefully. This is a natural phenomenon that can be modelled by a decay function. The reason is that, after every hour we expect the medicine in the blood to keep reducing.
Therefore we use the decay function rather. This is given by,
where,
and
On substitution, we obtain;
Now, we take our calculators and look for the constant
,then type e raised to exponent of -1.4. If you are using a scientific or programmable calculator you will find this constant as a secondary function. Remember it is the base of the Natural logarithm.
If everything goes well, you should obtain;
This implies that,
Therefore after 10 hours 24.66 mg of the medicine will still remain in the system.
The expression is,
But we have to analyze the problem carefully. This is a natural phenomenon that can be modelled by a decay function. The reason is that, after every hour we expect the medicine in the blood to keep reducing.
Therefore we use the decay function rather. This is given by,
where,
and
On substitution, we obtain;
Now, we take our calculators and look for the constant
,then type e raised to exponent of -1.4. If you are using a scientific or programmable calculator you will find this constant as a secondary function. Remember it is the base of the Natural logarithm.
If everything goes well, you should obtain;
This implies that,
Therefore after 10 hours 24.66 mg of the medicine will still remain in the system.