real zeros of function algebraically

Question

Find all the real zeros of the function algebraically. (Enter your answers from smallest to largest.

f(x) = x² + 6x + 9

f(x) = x⁴ + 4x³ – 21x²

Answer 1

The first one factors as (x+3)(x+3) = 0

So x=-3 is a zero of multiplicity 2

The second one factors as (x^2) (x^2 + 4x - 21)

x^2( x + 7 )( x - 3 )

The zeros are x=0 of multiplicity 2, x=-7 and x=3