Mathematics
7 Online
OpenStudy (anonymous):
What is the remainder when (x3 − 6x2 − 42x + 79) is divided by (x + 5)?
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OpenStudy (welshfella):
use reminder theorem
The remainder when P(x) is divided by (x - a) = f(a)
OpenStudy (welshfella):
so here you need to find P(-5)
OpenStudy (anonymous):
i tried plugging in -5, but i kept getting numbers that weren't in the answer choices
OpenStudy (welshfella):
(P(x) is your polynomial)
OpenStudy (welshfella):
oh maybe the choices are all wrong
i'll see what i get
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OpenStudy (anonymous):
okay thank you
OpenStudy (welshfella):
i get 14
OpenStudy (welshfella):
f(-5) = -125 - 150 - (42*-5) + 79
OpenStudy (anonymous):
thats one of the answer choices! and i was doing +150 idk why lol oops
OpenStudy (anonymous):
can you help me with one more
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OpenStudy (welshfella):
ok
OpenStudy (anonymous):
Describe the graph of the function f(x) = x3 − 11x2 + 36x − 36. Include the y-intercept, x-intercepts, and the end behavior.
OpenStudy (welshfella):
well the y-intercept occurs when x = 0
so find f(0) and you get that one
OpenStudy (anonymous):
okay, is the end behavior down?
OpenStudy (welshfella):
hold on
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OpenStudy (anonymous):
and i got -36 for the y-intercept
OpenStudy (welshfella):
right
OpenStudy (anonymous):
yay
OpenStudy (welshfella):
its been a while since i did end behaviours
fo find the x intercepts we need to solve
x^3 -11x^2 + 36x - 36
OpenStudy (anonymous):
So set it equal to 0?
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OpenStudy (welshfella):
yes
OpenStudy (welshfella):
as the last number is 36 we could try 2,3 and 6 to see if they are roots
OpenStudy (anonymous):
Can there be more than one answer when you do that tho
OpenStudy (welshfella):
f(2) = 8 - 44 + 72 - 36 = 0
yes x=2 is one x-intercept
OpenStudy (anonymous):
i think they all work
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OpenStudy (welshfella):
yes they do
thats is pure luck!!!!
OpenStudy (welshfella):
lol
OpenStudy (anonymous):
I think the end behavior is down because it hits x at 3 points
OpenStudy (welshfella):
normally i would divide the polynomial by x - 2 and try to factor the quotient
OpenStudy (welshfella):
no i dont think we can say that
as the last zero is 6 try finding f(7) and f(8) and see if they are increasing or decreasing
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OpenStudy (welshfella):
f(7) = 20 f(8) = 60
so end behaivour is increasing
OpenStudy (anonymous):
so up? lol
OpenStudy (welshfella):
yes
OpenStudy (anonymous):
yay! thank you so much!
OpenStudy (welshfella):
i'll draw the graph on my calculator to confirm
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OpenStudy (welshfella):
yep it looks somthing like
|dw:1438439995445:dw|