A polynomial of degree 3, P ( x ) has leading coefficient 1, and has roots of -5 i , − -5 i and 4

Answer 1

(x-4)(x^2+25) = x^3 -4x^2 +25x -100

but you want degree 3, so just multiply by 3 to get

3x^3 -12x^2 +75x -300

or 3(x-4)(x^2+25) in factored form or

3(x-4)(x-5i)(x+5i)