# Homework Help: Polynomial functions, descartes rule

1. Dec 3, 2007

### viet_jon

[SOLVED] polynomial functions, descartes rule

1. f (–x) = (–x)^5 – (–x)^4 + 3(–x)^3 + 9(–x)^2 – (–x) + 5

2. Relevant equations

3. = –x^5 – x^4 – 3x^3 + 9x^2 + x + 5

but isn't a negative x a negative suppose to = positive?

so shouldnt – (–x)^4 = x^4 instead of – (–x)^4 = -x^4 ?

Last edited: Dec 3, 2007
2. Dec 3, 2007

### rs1n

No, because you must follow the order of operations:

$$-(-x)^4 = -[ (-x)^4] = -[x^4] = -x^4$$

Parentheses come first, then exponentiation, then negation (in this problem).

3. Dec 3, 2007

### viet_jon

ok...hehhe...I'ma dumbass.....

can't believe I missed that

thnkx. cheers

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