Respuesta :

calculista
we know that

 The difference of two squares is a squared number subtracted from another squared number. Every difference of squares may be factored according to the identity

(A²-B²)=(A+B)*(A-B)
so 

the answer is 
49m2 − 81n4

49m2 − 81n4=(7m+9n²)*(7m-9n²)