完全平方公式 1.(4m-1/2n)(1/2n-4m).2.(3a+5)^2-(2a-7)^2 3.(x+y)(x-y)-(2x-y)^2

问题描述:

完全平方公式 1.(4m-1/2n)(1/2n-4m).2.(3a+5)^2-(2a-7)^2 3.(x+y)(x-y)-(2x-y)^2

1.(4m-1/2n)(1/2n-4m)=-(4m-1/2n)²=-(16m²-4mn+1/4n²)=-16m²+4mn-1/4n²2.(3a+5)^2-(2a-7)^2 =9a²+30a+25-4a²+28a-49=5a²+58a-243.(x+y)(x-y)-(2x-y)^2=x²-y²-4...