Mathematics
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OpenStudy (anonymous):
Limitquestion
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OpenStudy (anonymous):
So as x -> -3
OpenStudy (anonymous):
\[\frac{ x^2-9 }{ x^3 + 3}\]
OpenStudy (anonymous):
I know I can factor the top a little like (x-3)(x+3)
OpenStudy (amistre64):
you can factor the bottom as well
OpenStudy (amistre64):
sum of cubes
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OpenStudy (amistre64):
or if anything
you now x-3 is a factor, so divide it out of it
OpenStudy (amistre64):
err, x+3 that is :)
OpenStudy (anonymous):
Would the sum of cubes look like this?
(x + 3)(x^2 - cuberoot(3)x + squareroot(3) ) ?
OpenStudy (anonymous):
did you try and plug in the number first?
OpenStudy (amistre64):
-3x
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OpenStudy (amistre64):
(a+b)(a^2+b^2-ab)
a(a^2+b^2-ab) +b(a^2+b^2-ab)
a^3+abb -aab +aab+b^3-abb
a^3 -aab +aab+b^3 etc ...
OpenStudy (anonymous):
So purple math describes sum of cubes as
"a^3 + b^3 = (a + b)(a^2 – ab + b^2)
a^3 – b^3 = (a – b)(a^2 + ab + b^2)"
a = x
b = 3 or cuberoot(3) ?
OpenStudy (amistre64):
ima just wolf it to avoid my typos
OpenStudy (anonymous):
or just plug in the number and realize you get 0 and avoid that
which is the answer
OpenStudy (anonymous):
x^3 + 3
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OpenStudy (anonymous):
Yeah trying to do it algebraically though @Austin6i6
OpenStudy (anonymous):
Instead of direct subsitution
OpenStudy (amistre64):
-27+9 aint zero, so yeah
OpenStudy (anonymous):
whats the numerator @amistre64
OpenStudy (anonymous):
^^^
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OpenStudy (anonymous):
0
OpenStudy (amistre64):
i was thinking the bottom was zero for some reason lol
OpenStudy (anonymous):
whats 0/ any number @amistre64
OpenStudy (anonymous):
0
OpenStudy (anonymous):
Aiight algebraically is too much
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OpenStudy (amistre64):
hey, if they wanted me to pay attention in elementary school, they wouldnt have had all the girls around :)
OpenStudy (anonymous):
Im just going to direct subsitution
OpenStudy (anonymous):
problem is done, i guess if you want to practice, but its really pointless because thats how all mathematicians will do it.
OpenStudy (amistre64):
it algebraic enough,
OpenStudy (anonymous):
Ye
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OpenStudy (amistre64):
if (x+3) was a factor on the bottom, and it aint
we get: (x^3+9)= (x+3)(x^2 -3x +9) -18
OpenStudy (amistre64):
if the remainder was 0, not -18 then we would have had an issue