Not that Complicated

Algebra Level pending

( z + 2 3 ) 2 + 3 ( 2 z 3 ) 2 = 4 ( 4 z 2 3 ) \large (\sqrt[3]{z+2})^2+3(\sqrt[3]{2-z})^2=4(\sqrt[3]{4-z^2})

Find the sum of all integer values of z z satisfying the equation above.


The answer is 0.

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1 solution

Let a = z + 2 3 a=\sqrt[3]{z+2} and b = 2 z 3 b=\sqrt[3]{2-z} . Then, we know that a 2 + 3 b 2 = 4 a b a^2+3b^2=4ab . ( a b ) ( a 3 b ) = 0 a = b (a-b)(a-3b)=0\implies{a=b} or a = 3 b a=3b . By substituting back the values, we obtain z + 2 3 = 2 z 3 \sqrt[3]{z+2}=\sqrt[3]{2-z} or z + 2 3 = 3 ( 2 z 3 ) \sqrt[3]{z+2}=3(\sqrt[3]{2-z}) . Cubing both sides of the equation results in z + 2 = 2 z z+2=2-z or z + 2 = 27 ( 2 z ) z+2=27(2-z) . z = 0 \therefore{z=0} or z = 1 6 7 z=1\frac{6}{7} , the required integer solution is z = 0 z=0 .

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