Let the required zeroes be \(α\) , \(β\)

\(α + β = \frac{21}{8} = \frac{42}{16} = \frac{-b}{a}\) \(... (1)\)

\(αβ = \frac{5}{16} = \frac{c}{a}\) \(... (2)\)

From (1) and (2),

\(b = -42\) , \(a = 16\) , \(c = 5\)

Required polynomial is

\(16x^2 - 42x + 5 \)