(a+b-c)^2=?(x+y-z)(x-y+z)=?x-y=2,x^2-y^2=10,x+y=?(x+1/4)(x+3/4)=x^2+ax+3/16,a=?(x+y)^2(x^2-2xy+y^2)=( ? )^2=?(a-b)^2=(a+b)^2-?
热心网友
1:(a+b-c)^2=(a+b)^2-2c(a+b)+c^2=a^2+b^2+c^2+2ab-2ac-2bc2:(x+y-z)(x-y+z)=[x+(y-z)][x-(y-z)]=x^2-(y-z)^2=x^2-y^2-z^2+2yz3:因为x^2-y^2=(x+y)(x-y)=10,而x-y=2,所以x+y=54:x^2+x+3/16=x^2+ax+3/16,比较系数得:a=15:(x+y)^2(x^2-2xy+y^2)=(x+y)^2(x-y)^2=[(x+y)(x-y)]^2=(x^2-y^2)^2=x^4-2x^2y^2+y^46:(a-b)^2=a^2+b^2-2ab=a^2+b^2+2ab-4ab=(a+b)^2-4ab