例、计算: (1)(2x+3)2(2x-3)2 (x-3)x+3)(x2+9) (2x+3)(2x-3) (x2-9)(x2+9) (4x2-9) =x4-81 =16x4-72x2+81 (3)(x+y-4)(x+y+4 =(x+y)-4(x (x+y)2-42n)+4 x2+2xy+y2-16 (4)(2+1)22+1)24+1②204+1)+1 =(2-1)(2+1)(22+1)(2+1)…(2+1)+1 =(22-1)(22+1)(24+1)…(2+1)+1 (24-1)(24+1)…(2 64 +1)+1 (20-1)(2+1)+1=2128-1+1=2 128
例1、计算： (1)(2x+3)2 (2x-3)2 (2) ( 3)( 3)( 9) 2 x − x + x + 2 =[(2x +3)(2x −3)] 2 2 = (4x −9) 16 72 81 4 2 = x − x + ( 9)( 9) 2 2 = x − x + 81 4 = x − (3) (x + y − 4)(x + y + 4) (2 1)(2 1)(2 1) (2 1) 1 2 4 6 4 (4) + + + + + = (x + y) − 4(x + y) + 4 2 2 = (x + y) − 4 2 16 2 2 = x + xy + y − (2 1)(2 1)(2 1)(2 1) (2 1) 1 2 4 64 = − + + + + + (2 1)(2 1)(2 1) (2 1) 1 2 2 4 64 = − + + + + (2 1)(2 1) (2 1) 1 4 4 64 = − + + + (2 1)(2 1) 1 64 64 = − + + 2 1 1 128 = − + 128 = 2
课堂练习一 计算: ②(xy+1)(m-3y ①n-nm2-n2)m+ ③(a+b+3a-b-3) ④(-a-b+ca-b-c) ⑤ 3 3 x+2 y x-2y+
课堂练习一： (− a −b + c)(a −b − c) (m−n)(m −n )(m+ n) ① 2 2 2 2 ② (xy +1) (xy −1) ③ (a +b +3)(a −b −3) ④ − + + − 2 3 2 2 3 ⑤ x 2y x y 计算：