Answer:
(x+2)(x+4)
Explanation:
The x-coefficient (6) is the sum of the constants in the binomial factors, and the constant (8) is their product. To factor such an expression, you look for factors of 8 that sum to 6.
8 = 1·8 = 2·4
The latter two add to give 6: 2+4 = 6. So, the factorization is ...
x^2 +6x +8 = (x +2)(x +4)