Respuesta :

Answer:

Step-by-step explanation:

(3a-7)²=(3a-7)(3a-7)

= 9a²-21a-21a+49

= 9a²-42a+49

Therefore the error in that answer is -42a was replaced with -21a.

Answer:

(3a-7)²=(3a-7)(3a-7)

= 9a²-21a-21a+49

= 9a²-42a+49

Step-by-step explanation: