How to Factor (x^6)-(y^6) using difference of squares?
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OpenStudy (anonymous):
\[x^6-y^6\]
OpenStudy (aum):
\[
x^6 - y^6 = (x^3)^2 - (y^3)^2 = ?
\]
OpenStudy (aum):
\[ a^2 - b^2 = (a+b)(a-b)\]
OpenStudy (anonymous):
I got \[(x^3-y^3)(x^3+y^3) \]
but how would factor this even further?
OpenStudy (anonymous):
is that wrong?
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OpenStudy (aum):
That is correct. That is the first step. Then you can factor further by using the following identities:
\[
a^3 - b^3 = (a-b)(a^2 + ab + b^2) \\
a^3 + b^3 = (a+b)(a^2 - ab + b^2)
\]
OpenStudy (anonymous):
oh okay the difference of cubes, thats whats i was missing i think,
OpenStudy (anonymous):
wait hold on, how would i go about plugging \[(x^3-y^3)(x^3+y^3)\]
OpenStudy (anonymous):
into the identity
OpenStudy (freckles):
replace a with x and replace y with b
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OpenStudy (anonymous):
so I just do this:
\[(x-y)^3(x+y)^3=((x-y)-(x+y)((x-y)^2+(x-y)(x+y)+(x+y))\]
OpenStudy (anonymous):
and then simplify
OpenStudy (freckles):
didn't you have
\[(x^3-y^3)(x^3+y^3)?\]
OpenStudy (anonymous):
yes
OpenStudy (freckles):
use what aum gave you to factor more
\[a^3 - b^3 = (a-b)(a^2 + ab + b^2) \\ a^3 + b^3 = (a+b)(a^2 - ab + b^2)\]
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OpenStudy (freckles):
like you can factor x^3-y^3 more by saying (x-y)(x^2+xy+y^2)
now you need to factor x^3+y^3