Answer:
Explanation:
Third level polynomial, so three factors
Only whole numbers, so only whole number x⁰ factors
whole number factors of 3 are 1,1,3 or 1,-1,-3 or -1,-1,3
let's try (x + 3) as a factor
  x² + 2x + 1  
x + 3 | x³ + 5x² + 7x + 3
 - x³ + 3x²
 2x² + 7x
 - 2x² + 6x
 x + 3
 - x + 3
 0
so (x + 3) is a factor and x² + 2x + 1 factors to (x + 1)²
x³ + 5x² + 7x + 3 = (x + 3)(x + 1)(x + 1)