Question

Check, whether 1 is the zero of the polynomial 9x3 - 5x + 20.

Answer 1

No as 9×3=27-5+20=42 which is not equal to zero..

Answer 2

let p(x) be the given polynomial

$p(x) = 9 {x}^{3} - 5x + 20 \\ p(1) = 9(1) {}^{3} - 5(1) + 20 \\ p(1) = 9 - 5 + 20 \\ p(1) = 24$
x = 1 is not zero of p(x)