已知x=-4,y=1/4,求x的平方乘以x的2n次方乘以y的2n+2次方?
x^2*x^(2n)*y^(2n+2)
＝x^(2n+2)*y^(2n+2)
＝（xy)^(2n+2)
＝（-4×1/4）^（2n+2)
＝1