Let f: C -> C be the function given by

f(z) = ( 7- 11i )^2 z^3 + 6z^2 - (4 + i ) z - 8/3

Then the complex number cos pi/7 + i sin pi/7 belongs to the image of f.

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This looks really simple but is so difficult to do as the computations go nowhere.. or it may be pretty elementary and I have just not started it out right!