1 (x^2-y^2)-(x-y)^22 3(x^2-27)-四分之三x^23 x^2n-9^n另外一题加5分_数学解答

1 (x^2-y^2)-(x-y)^2
2 3(x^2-27)-四分之三x^2
3 x^2n-9^n
另外一题加5分

人气：319 ℃　时间：2020-01-28 05:12:31

解答

1 (x^2-y^2)-(x-y)^2=(x+y)(x-y)-(x-y)^2=(x-y)[x+y-(x-y)]=2y(x-y)2 3(x^2-27)-3/4x^2=3(x^2-27-1/4x^2)=3(3/4x^2-27)=3*3(1/4x^2-9)=9(1/2x+3)(1/2x-3)3 x^2n-9^n=n(x^2-9)=n(x+3)(x-3)