Plz show me step by step how to solve these equations ASAP. Tysm!

13. x^6-64x^4+x^2-7x-51; x=8

14. -x^3+3x^2+5x+1; x=-12

15. 2x^3+4x^2+6x+7; x=1/2

(btw, 13, 14, and 15 are not a part of the equation)
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