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Mathematics 16 Online
OpenStudy (anonymous):

Limitquestion

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

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

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

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):

^^^

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

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

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

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