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OpenStudy (zarkon):
42?
OpenStudy (campbell_st):
find the value of the expression\[\frac{a^{32} -b^{32}}{(a^2 + b^2)(a^4 + b^4)(a^8 + b^8)(a^{16} + b^{16})} + 12b\] if the only thing known about a and b is that
a + b = 6
myininaya (myininaya):
eww
OpenStudy (zarkon):
36
myininaya (myininaya):
\[a+b=6 \\ (a+b)^2=36 \\a^2+2ab+b^2=36 \\ a^2+b^2=36-2ab \\ (a+b)^4=1296 \\ a^4+4a^3b+6a^2b^2+4ab^3+b^4=1296 \\ a^4+b^4=1296-4a^3b-6a^2b^2-4ab^3\]
blah blah
this seems like an awful long way
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myininaya (myininaya):
maybe we can factor the top and see if something cancels
OpenStudy (campbell_st):
@Zarkon you need a group for yourself above champion, perhaps demigod
OpenStudy (zarkon):
the numerator factors nicely
OpenStudy (zarkon):
difference of squares (over and over)
myininaya (myininaya):
\[a^{32}-b^{32}=(a^{16}-b^{16})(a^{16}+b^{16}) \\ =(a^4-b^4)(a^4+b^4)(a^{16}+b^{16})\]
little annoying using that over and over
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