Respuesta :

Answer:

(x+3)(x+7)

Step-by-step explanation:

Answer:

(x + 3)(x + 7).

Step-by-step explanation:

x^2 + 10x + 21.

You need  2 numbers whose product is the last number in the function (+21) and whose sum is the coefficient of x (+10).

These are + 3 and + 7, so the factors are:

(x + 3)(x + 7).