Prove all real polynomials of degree $n(n \geq 1)$ can be factorized to the product of k linear factors and l quadratic factors

Question

Prove all real polynomials of degree $n(n \geq 1)$ can be factorized to the product of k linear factors and l quadratic factors following holds

1. $k$ and $l$ are integers ($k \geq 1, l \geq 0$)
2. All linear factors and quadratic factors are real polynomial
3. Every quadratic factor has no real root($b^2-4ac < 0$ at $ax^2+bx+c)$

How can I prove this? It seems that I can use mathematical induction but I have no idea about details.