zhiliaoying
幼苗
共回答了16个问题采纳率:87.5% 举报
a²-a-a²-2a+1=a²-a-a²+2a-1
=a-1
(5a-4b)²-2(5a-4b)(3a-2b)-(-a+2b)(-a-2b)
=(5a-4b)²-(5a-4b)(6a-4b)-(a-2b)(a+2b)
=(5a-4b)(5a-4b-6a+4b)-(a-2b)(a+2b)
=-a(5a-4b)-a^2+4b^2=5a^2-4ab-a^2+4b^2=4a^2-4ab+4b^2=4(a+b)^2-12ab=4+12*2=28
结果=2(xy)^2(x^2+y^2)=2(xy)^2(x^2-2xy+y^2+2xy)=2*3*3*(1+2*3)=126
1年前
2