The formula used: A2-B2 = (a+b) (a-b) A2-2ab+B2 = (a-b) 2a2+2ab+B2 = (a+b) 2.

(3) The original formula = (x2-3 2) (x2+3 2) = (x2) 2-(3 2) 2 = x4-81.

(4) The original formula = [x+(y-z)] [x-(y-z)] = x 2-(y-z) 2.

16.

(1) The original formula = 9a2-12ab+4b2 = (3a) 2-12ab+(2b) 2 = (3a-2b) 2.

(2) The original formula = x (x2-2xy+y 2) = x (x-y) 2.

(3) original formula = (x-y) 3 [a2-(2b) 2] = (x-y) 3 (a-2b) (a+2b)

(40 Formula = (2A) 4-1= [(2A) 2] 2-1= [(2A) 2-1] [(2A) 2+1] = [2A-65438]