Mathematics
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OpenStudy (anonymous):
Please tell me if f(x) = x^3 + 0.04x^2 + 3 is odd, even or niether (then tell me how you found out)
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OpenStudy (anonymous):
Hey jim!!
jimthompson5910 (jim_thompson5910):
hey
jimthompson5910 (jim_thompson5910):
Hint: if f(-x) = f(x), then the function is even
OpenStudy (anonymous):
I'm doin' good in class. Your help on my math packet got me some good brownie points :)
jimthompson5910 (jim_thompson5910):
if f(-x) = -f(x), then the function is odd
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OpenStudy (anonymous):
right. But I'm not sure how to show it
jimthompson5910 (jim_thompson5910):
so first, let's find f(-x)
OpenStudy (anonymous):
does f(-x) = -x^3 -0.04x + 3
jimthompson5910 (jim_thompson5910):
f(x) = x^3 + 0.04x^2 + 3
f(-x) = (-x)^3 + 0.04(-x)^2 + 3
f(-x) = -x^3 + 0.04x^2 + 3
jimthompson5910 (jim_thompson5910):
keep in mind that (-x)^2 = x^2
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jimthompson5910 (jim_thompson5910):
so does f(-x) = f(x)???
OpenStudy (anonymous):
but not (-x)^3
jimthompson5910 (jim_thompson5910):
(-x)^3 = (-x)*(-x)*(-x) = -x^3
OpenStudy (anonymous):
so f(-x) does not = f(x)
jimthompson5910 (jim_thompson5910):
yep
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jimthompson5910 (jim_thompson5910):
which means that f is not an even function
OpenStudy (anonymous):
so it's neither ?
jimthompson5910 (jim_thompson5910):
now what about f(-x) = -f(x)?
OpenStudy (anonymous):
F IS NOT EVEN A FUNCTION? Omg dude
OpenStudy (anonymous):
lol
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jimthompson5910 (jim_thompson5910):
huh
OpenStudy (anonymous):
just kidding around
OpenStudy (anonymous):
f(-x) = -x^3 - 0.04x - 3?
jimthompson5910 (jim_thompson5910):
we can refer to f(x) as f, I've seen it plenty of times
OpenStudy (anonymous):
I'm not sure how to show f(-x) = -f(x)
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jimthompson5910 (jim_thompson5910):
negate everything in f(x) to get -f(x)
jimthompson5910 (jim_thompson5910):
-f(x) = -1*f(x)
jimthompson5910 (jim_thompson5910):
So if f(x) = x^3 + 0.04x^2 + 3, then -f(x) = -1*f(x) = -1(x^3 + 0.04x^2 + 3)
jimthompson5910 (jim_thompson5910):
then you distribute and simplify
OpenStudy (anonymous):
neither instantly and with your eyeballs
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OpenStudy (anonymous):
so it would be -x^3+0.04x^2+3 = -x^3-0.04x^2-3. so it is neither.
OpenStudy (anonymous):
\[f(x) = x^3 + 0.04x^2 + 3 \] has both even and odd powers, so neither
jimthompson5910 (jim_thompson5910):
yep you got it
OpenStudy (anonymous):
thanks jim :)
jimthompson5910 (jim_thompson5910):
yw