SOLUTION: Show that 1/2 is a root of the polynomial expression 2x^3+5x^2-39x+18

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Question 909502: Show that 1/2 is a root of the polynomial expression 2x^3+5x^2-39x+18
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
IF 1%2F2 is a root, then evaluation of the polynomial for x=1%2F2 would be 0.

2%281%2F2%29%5E3%2B5%281%2F2%29%5E2-39%281%2F2%29%2B18;
Is this equal to 0 ?
2%2F8%2B5%2F4-39%2F2%2B18

1%2F4%2B5%2F4-78%2F4%2B18

%286-78%29%2F4%2B18

-72%2F4%2B18

-18%2B18=0---------Yes, 1%2F2 is a root for the given polynomial.