show that {1,2} ⊆ {x|x^4 - x^3 - x^2 - 5x + 6 = 0} Sent from my iPhone using Tapatalk

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$1^4 - 1^3 - 1^2 - 5(1) + 6 = 1-1-1-5+6 = 7-7=0$ $2^4 - 2^3 - 2^2 - 5(2) + 6 = 16 - 8 - 4 - 10 + 6 = 22-22=0$