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Due to the fact that this is a piecewise function, we're going
to take the derivative.
So Y prime equal -2 X -9.
We're going to look at that derivative when we set it equal
to 0.
So if we set -2 X -9 equal to 0, we're going to get -9 halves.
We're going to take the second piece of the original function,
the derivative -2 X +3 and we're going to set it equal to 0.
So X equal 3 halves.
Now we have to figure out at one, is it a smooth continuous
curve?
Does the limit as X goes from one to the left equal the limit
as X goes to one from the right?
It could be a defined point, but if it's not a smooth point, it
doesn't have a derivative there and hence it be undefined.
And that would be an example of like a corner or a cusp.
So when we stick in one from the left, we get a -11 and when we
stick in one from the right, we get one.
So Y prime of 1 does not exist.
So our three points that we need to check out are -9 halves,
three halves and one.
When I put that on the number line, if I look to the right of
three halves, I'm going to use the bottom equation.
Say we put in five, we're going to get a negative to the right
of three halves.
Three halves has an odd multiplicity.
So if it's negative on one side, it's got to be positive on the
other.
So between 1:00 and 3:00 halves, it's positive.
Now in between -9 halves and one, we have to use the correct
derivative, which is that top equation, because we need to be
less than or equal to one.
If we put in a value, say zero there, we end up with -9 So we
know between -9 halves and one, we're going to be negative
because of the multiplicity.
On the other side of -9 halves, we're going to be positive.
So if we look at it that and we think about the original
function between negative Infinity and -9 halves, we've
got to be increasing from -9 halves to one, we've got to be
decreasing.
From one to three halves, we've got to be increasing.
From three halves to Infinity, we've got to be decreasing.
So we need to actually find the original function values at
those locations.
So F and -9 halves is going to be 93 fourths, making sure to
use the top equation F of one.
Once again, we're going to use the top equation is -7 and F of
three halves using the bottom equation because I needed X
greater than one is -27 fourths.
So our critical points where the F prime was undefined is that X
equal 1 our our X values where the first derivative of 0 is -9
halves and three halves.
Our local Max increasing to decreasing is at -9 halves, 93
fourths and three halves -27 fourths, and our local min
decreasing to increasing is at one -7.