Question

(c2+d2)3-3c2d2(c2+d2)
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Answer 1

$\displaystyle\bf\\(c^{2} +d^{2} )^{3} -3c^{2} d^{2} (c^{2} +d^{2})=(c^{2} )^{3} +3c^{4} d^{2}+3c^{2} d^{4} +(d^{2} )^{3}-3c^{4}d^{2} -3c^{2} d^{4}=\\\\=c^{6}+d^{6}$