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Mathematics 22 Online
zarkam21:

??

zarkam21:

1 attachment
zarkam21:

1 attachment
Vocaloid:

for part I the max number of roots is equal to the degree

zarkam21:

3?

Vocaloid:

the degree is the highest exponent

zarkam21:

4

Vocaloid:

good for part IIa) count the sign changes in H(x)

zarkam21:

3?

Vocaloid:

|dw:1516218132719:dw|

Vocaloid:

|dw:1516218137905:dw|

Vocaloid:

so 4 maximum positive real roots

zarkam21:

okay so for part iii a\[4(-x)^4-5(-x)^3+2(-x)^2+x+5\]

Vocaloid:

good, now simplify this and count the number of sign changes in the simplified expression

zarkam21:

um 2?

Vocaloid:

4x^4 + 5x^3 + 2x^2 + x + 5 ^ how many sign changes?

zarkam21:

not 2?

Vocaloid:

no, not 2 count the number of sign changes in the above expression

zarkam21:

from the original right?

Vocaloid:

\(\color{#0cbb34}{\text{Originally Posted by}}\) @Vocaloid 4x^4 + 5x^3 + 2x^2 + x + 5 ^ how many sign changes? \(\color{#0cbb34}{\text{End of Quote}}\)

Vocaloid:

the one after we plugged in (-x)

zarkam21:

4

Vocaloid:

notice how all the signs are positive

zarkam21:

yeah

Vocaloid:

so how many sign changes are there if they all are positive?

zarkam21:

1

zarkam21:

\(\color{#0cbb34}{\text{Originally Posted by}}\) @Vocaloid 4x^4 + 5x^3 + 2x^2 + x + 5 ^ how many sign changes? \(\color{#0cbb34}{\text{End of Quote}}\)

zarkam21:

after the 4x^4 it is a positive that's all i see

Vocaloid:

a sign change is defined as an instance where the sign changes from + to - or from - to + with that being said, how many sign changes are there?

zarkam21:

3

Vocaloid:

the first term is positive the second term is positive (so no change) the third term is positive (still no change) the fourth term is positive (still no change) so how many sign changes?

zarkam21:

1

zarkam21:

Ugh sorry

Vocaloid:

remember, for a sign change the sign has to switch from + to - or from - to +

Vocaloid:

so if they are all + how many sign changes?

zarkam21:

\(\color{#0cbb34}{\text{Originally Posted by}}\) @Vocaloid the first term is positive the second term is positive (so no change) the third term is positive (still no change) the fourth term is positive (still no change) so how many sign changes? \(\color{#0cbb34}{\text{End of Quote}}\)

zarkam21:

From this 1

Vocaloid:

notice how all the terms are positive for something to count as a sign change, the sign MUST change from + to - or from - to + but notice how we don't have any negative signs, so there must be __ sign changes

zarkam21:

zero

Vocaloid:

good, zero sign changes and zero possible roots for c) since total roots = 0 and positive roots can be at most 4, if we consider complex roots as doubles there can be either 4, 2, or 0 complex roots

zarkam21:

so 4,2,0

Vocaloid:

yes

zarkam21:

okay so for part IV

zarkam21:

would it be the same answer?

Vocaloid:

c) should be 0 negative roots, IV should be 4/2/0 complex roots

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