1.-25x2y2+1002.(2a-5b)2-9a2因式分解计算下列各式:(1)(2a+1)2=______(2)(3m-2n)2=_________;(3)-(xy-3)2=________;(4)-(0.5m+2)2=__________.4a2+4a+19m2-12mn+4n2-x2y2+6xy-9-0.25m2-2m-4探究反过来:4a2+4a+1=(2a+1)29m2-12mn+4n2=(3m-2n)2-x2y2+6xy-9=-(xy-3)2-0.25m2-2m-4=-(0.5m+2)2探究判断下列各式能否用完全平方公式进行因式分解:91525)2(2aa222)3(yabx2244)6(yxyx224126)7(nmnm229124)5(baba1)23(2)23()8(2yxyx2249)4(yx(1)例1把下列各式分解因式:aaxxyyaxaxyay222222141292443363bb+9262)4(2yxyx)()(2))(5(2abmbamba222510)1(yxyx229341)2(nmnm91344)4(2aa322344)5(xyyxyx2241)3(baba练习:把下列各式分解因式:1)(22)(121)6(2baba例2分解因式:(2)16x4-8x2+1222121)1(baba例3分解因式:22216)4)(1(xx42242)2(yyxx练习:把下列各式因式分解:222)1(4)1(xx(2)(a2-2)2-4(a2-2)+4用简便方法计算(1)49.92+9.98+0.12(2)99992+19999例41:分解因式(1)0.04a2+0.24a+0.36.(2)-ab+2a2b-a3b(3)x4-18x2+81.(4)(6)(5)(7)(4a2+1)2-16a22)(4)(129baba2:用简便方法计算2220054010200320032:(m2+n2)(m2+n2–10)+25=0,求m2+n23:4x2+y2-4xy-12x+6y+9=0求x,y关系5:分解因式:m4+4选做题(A)4:993-99能被100整除吗?你是怎样想的?1:分解因式(1)y2-4x(y-x);(2)(a+b)2-4(a+b-1)(3)(x+y)2-2(x2-y2)+(x-y)2.03)..11622.2054212222222的形状试判断,且满足三边长,是的、、已知(请说明理由为什么?的值总是正数式取任何有理数时,多项、)当(的值,求)已知(ABCcabcabcbaABCcbayxyxyxbababa选做题(B)