Question

determine whether the indicated real number is a zero of the polynomial function f.
1; f(x)=5x^3-18x^2+21x-8

Answer 1

so you just plug it in
\[f(1)= 5(1)^{3} - 18(1)^{2} +21(1) - 8\]
start reducing
\[5(1) - 18(1) + 21(1) - 8\]
and some more
\[5 - 18 + 21 - 8\]
and
\[-13 + 21 - 8\]
and
\[7 - 8\]
finally
\[f(1) = -1\]

Therefore the number is not a zero of the function