4(x+2y)^2-9(x-y)^2=[2(x+2y)+3(x-y)][2(x+2y)-3(x-y)] (平方差公式)
=-(5x+y)(x-7y)
x^(n+3)-x^(n-1)=x^(n-1)(x^4-1) (提取公因式的最低次方)
=x^(n-1)(x^2+1)(x^2-1) (平方差公式)
=x^(n-1)(x^2+1)(x-1)(x +1) (平方差公式)
4(x+2y)^2-9(x-y)^2=[2(x+2y)+3(x-y)][2(x+2y)-3(x-y)] (平方差公式)
=-(5x+y)(x-7y)
x^(n+3)-x^(n-1)=x^(n-1)(x^4-1) (提取公因式的最低次方)
=x^(n-1)(x^2+1)(x^2-1) (平方差公式)
=x^(n-1)(x^2+1)(x-1)(x +1) (平方差公式)