几道简单的整式计算,尽量写清楚一点计算:(1-x)(0.6-x)(2x+y)(x-y)(2n+5)(

几道简单的整式计算,尽量写清楚一点计算:(1-x)(0.6-x)(2x+y)(x-y)(2n+5)(

原式=0.6-x-0.6x+x2=x2-1.6x+0.6原式=2x2-2xy+xy-y2=2x2-xy-y2原式=2n2-6n+5n-15=2n2-n-15原式=acx2+adx+bcx+bd=acx2+(ad+bc)x+bd原式=(x2-2xy-xy+2y2)-(1/2)(2x2+4xy-3xy-6y2)=(x2-3xy+2y2)-(1/2)(2x2+xy-6y2)=x2-3xy+2y2-x2-(1/2)xy+3y2=-(7/2)xy+5y2将x=2,y=5带入得：-(7/2)*2*5+5*5*5=90======以下答案可供参考======供参考答案1:(1)0.6-1.6x+x^2(2)2x^2-xy-y^2(3)2n^2-n-15(4)acx^2+(ad+bc)x+bd(5)原式=(x^2-3xy+2y^2)-(1/2) (2x^2+xy-6y^2) =-(7/2)xy+5y^2当x=2, y=5时,原式=-(7/2)*2*5+5*5^2 =90供参考答案2:(1-x)(0.6-x)=0.6-X-0.6X+X^=X^-(1+0.6)X+0.6=X^-1.6X+0.6(2x+y)(x-y) =2x^-2xy+xy-y^=2x^-(2-1)xy-y^=2x^-xy-y^(2n+5)(n-3)=2n^-6n+5n-15=2n^-(6-5)n-15=2n^-n-15(ax+b)(cx+d) =ax^+adx+bcx+bd=ax^+(ad+bc)x+bd(x-y)(x-2y)- (1/2) (2x-3y)(x+2y)=[2(x-y)(x-2y)- (2x-3y)(x+2y)]/2=(2x^-2xy-xy+2y^-2x^-4xy+3xy+6y^)/2=[(-2-1-4+3)xy+6y^]/2=(-4xy+6y^)/2=[2(3y^-2xy)]/2=3y^-2xy把x=2, y=5的值代入上式3y^-2xy=3*5*5-2*2*5=75-20=55

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