[tex]x^6-64=0 \\ \\ (x^3 -8)(x^3+8)=0\\ \\(x^3-2^3)(x^3+2^3)=0\\\\(x-2)(x^2-2x+4) (x+2)(x^2+2x+4)=0 \\ \\ (x-2)(x+2)(x^2-2x+4) (x^2+2x+4)=0 \\ \\x-2=0 \ \ or \ \ x+2=0 \\ \\x=2 \ \ or \ \ x=-2 \\\\ (x^2-2x+4), \ \ (x^2+2x+4) - \ \ b^2-4ac =(-2)^2-4\cdot 1\cdot4 =4-16=-12 \\\\\ b^2-4ac <0, \ then \ roots \ are \ imaginary \ (non-real) [/tex]