一、复习乘法公式: 平方差公式: (a+b)(a-b) =_ 完全平方公式:(ab) 2 = _ 说一说(填空): (1)(a - - 2) 2 =( ) 2 - - 2( )( )+( ) 2 =( ) (2)(2a+3b) 2 =( ) 2 +2( )( )+( ) 2 =( )二、口算练习 (1)(a+6) 2 (2)(4+x) 2 =a 2 +12a+36 =16+8x+x 2 (3)(x-7) 2 (4) (8-y) 2 =x 2 -14x+49 =64-16y+y 2 (5)(3a+b) 2 ( 6)(4x+3y) 2 =9a 2 +6ab+b 2 =16x 2 +24xy+9y 2 (7)(-2x+5y) 2 (8)(-a-b) 2 =4x 2 -20 xy+25y 2 =a 2 +2ab+b 2 1. 运用完全平方公式计算 : (1) (1) (2 (2 x x +3 +3 y y ) ) 2 2 (3) (3) ( ( 7ab 7ab + + 2 2 ) ) 2 2 (2) (2) ( ( x x - 2 - 2 y y ) ) 2 2 (4) (4) (3 (3 a