Respuesta :

Answer:

81a^2+16b^2

Step-by-step explanation:

Answer:

Step-by-step explanation:

(−9a+4b)^2

= (−9a+4b)(−9a+4b)

= 81a^2 - 36ab - 36ab + 16b^2

= 81a^2 - 72ab + 16b^2