Respuesta :

x^2+10x+21

(x+3)(x+7)= 0

x^2+7x+3x+21= x^2+10x+21

x+3-3= 0-3

x+7-7= 0-7

Answers are :

x= -3 , x= -7

Answer:

x=-7,-3

Step-by-step explanation: