cupidxxx
幼苗
共回答了20个问题采纳率:80% 举报
1.(X+Y)^2-(X-Y)^2
=(X+Y+X-Y)(X+Y-X+Y)
=2X*2Y
=4XY
2.9(M+N)^2-(M-N)^2
=(3M+3N+M-N)(3M+3N-M+N)
=(4M+2N)(2M-4N)
=4(2M+N)(M-2N)
3.(M+N)^2-6(M+N)+9
=(M+N)^2-2*3(M+N)+3^2
=(M+N-3)^2
4.8XY(X-Y)-2(Y-X)^2
=-2((Y-X)^2-4XY(X-Y))
=-2(X-Y)(X-Y-4XY)
5.2AB-A^2*B^2-1+C^2
=2AB-(AB)^2-1+C^2
=C^2-((AB)^2-2AB+1)
=C^2-(AB-1)^2
=(C+AB-1)(C-AB+1)
6.-5X^3+5X^2+10X
=-5X(X^2-X-2)
=-5X((X-1/2)^2-9/4)
7.1*2+2*3=2*2^2 ,2*3+3*4=2*3^2 ,3*4+4*5=2*4^2……
规律是:
(n-1)n+n(n+1)=2*n^2
1年前
5