ending-behaviour-zeros-intermediate-value
X
00:00
/
00:00
CC
Hello wonderful mathematics people.
I'm Anna Cox from Kella Community College.
In behavior of a graph, Basically, what happens to the Y
when X goes to Infinity and when X goes to negative Infinity?
If we start with some polynomial function, F of X equal a sub NX
sub n + a sub n -, 1 X sub n - 1 plus...
plus a sub One X + a sub zero.
Our big important pieces here are the a sub N which is the
leading coefficient and the N which is the exponent.
It's the largest exponent of all of these terms being added and
or subtracted for the leading coefficient test.
If our a sub N is positive, then we know that if N is odd, if we
have a really, really big number to an odd power, it's still
going to be big.
And if we're multiply it by some positive, we're going to get a
big positive out towards Infinity.
Now, we don't know what's happening in between, nor do we
care, but we're going to look at what happens when we go out to
negative Infinity.
If I put a really, really, really big negative number in
and it's to an odd power, a negative to an odd is going to
be a negative.
If we then multiply it by a positive coefficient, that's
going to make a negative value when X goes out to negative
Infinity for my Y.
If we look at N is even, well, a big positive number to an even
power is positive.
And if you multiply it by a positive coefficient, it's still
positive.
I don't know what's going to happen in between if I take a
big negative number to an even power, a big negative to an even
power is positive, and positive times a positive coefficient is
going to be a positive.
So the black arrows represent what happens when X goes into
Infinity and negative Infinity to our Y value.
Now if the leading coefficient is negative, negative just
really means a reflection through the X axis.
So what's going to happen now is we're just going to flip the
arrows.
You could also think about it as a really really big positive
number to an odd powers positive.
But then if we multiply it by a negative coefficient, it turns
into a negative value.
I don't know what happens in between.
All I'm discussing is what happens between as X goes to
Infinity and negative Infinity.
The last one really big positive number to an even power is going
to be positive, but times a negative coefficient is going to
make that Y value go to a negative.
A really big negative number to an even power is positive.
Times a negative coefficient would give me a negative.
So the in behavior is what happens to the graph when we're
going out to Infinity and negative Infinity doesn't tell
me anything about what's occurring in between zeros of a
polynomial function factor.
The polynomial, then set each term equal to 0.
So if we're given some polynomial to factor, when we
have 4 terms, we're going to factor by grouping.
We're going to group the 1st 2 together and the second two
together.
If I take out an X ^2 from the 1st 2 terms, I get X - 5.
I'm going to take out a -4 from the 2nd 2 terms and get an X -,
5.
Now these new 2 terms.
So I went from 4 terms in the original to two terms.
These two terms each have an X -, 5 in common.
So using the distributive property, I'm going to pull it
out.
That leaves me an X ^2 - 4 X squared -4 is really just the
difference of squares.
So I get X -, 5 X -2 X +2.
So the zeros of the polynomial would be X is five when Y is 0X
is 2 when Y is 0X is -2 when Y is 0.
With multiple or with zeros we also have multiplicities.
And multiplicities just mean the degree of each of the terms.
So if we look, multiplicity is the power of the factor or the
exponent on each factored term.
So when we look at the example we just did, the multiplicity on
this 0 is going to be 1.
The multiplicity on 20 is 1.
The multiplicity on -2 zero is 1 because it's just the exponent
and if there is no number, it's understood to be a one.
If we had a new function, let's say F of X = -3 X cubed X -, 2
to the 4th, X + 7 to the 5th, and X - 3 to the first, the
zeros would be 00, 20, negative 70 and 30.
This was already as a monomial, it was already factored.
It was already just multiplication of terms, the
multiplicity of each term.
The multiplicity of the 00 would be 3 because that's the exponent
on the X.
The multiplicity OF20 would be 4, of -7 zero would be 5, and of
X -, 3 would be 1.
Intermediate value theorem.
If A is less than B and if F of A is less than 0 when F of B is
greater than 0, then there exists some C such that A is
less than C is less than B&F of C = 0.
So pictorially, if AF of A is A is less than B&F of A is
less than 0, and then BF of BF of B was greater than 0, What
this says is somewhere we have to cross the axis.
Now we may cross the axis multiple times.
We don't know how many, we just know that we have to cross it at
least once.
So here would be our C Here we'd have lots of different values of
CC1C2 and C3 would all be F of C = 0.
Thank you and have a wonderful day.
This is Anna Cox.