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(x的n次方+y的n次方)(x的n次方-y的n次方)-(x的n次方+y的n次方)²

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(x的n次方+y的n次方)(x的n次方-y的n次方)-(x的n次方+y的n次方)²
当x=2时,求代数式(1- x/3)(1+ x/3)(1+ x^2/3)(1+ x^4/81)的值
漏了,还有一题
m- 1/4(1-m)- 1/3m(2-m/4)
(x的n次方+y的n次方)(x的n次方-y的n次方)-(x的n次方+y的n次方)²
1、(x的n次方+y的n次方)(x的n次方-y的n次方)-(x的n次方+y的n次方)²
=(x^n+y^n)(x^n-y^n)-(x^n+y^n)^2
=(x^n)^2-(y^n)^2-[x^(2n)+2(x^n)*(y^n)+y^(2n)]
=x^(2n)-y^(2n)-x^(2n)-y^(2n)-2(x^n)*(y^n)
=-2y^(2n)-2(x^n)*(y^n)
2、(1- x/3)(1+ x/3)(1+ x^2/9)(1+ x^4/81)
=[1-(x/3)^2](1+x^2/9)(1+x^4/81)
=(1-x^2/9)(1+x^2/9)(1+x^4/81)
=(1-x^4/81)(1+x^4/81)
=1-x^8/2061
=1-2^8/2061
=1805/2061
3、m- 1/4(1-m)- 1/3m(2-m/4)
=m-(1/4)+(1/4)m-(2/3)m+(3/4)m^2
=(3/4)m^2-(1/4)+(5/4)m-(2/3)m
=(3/4)m^2+(7/12)m-(1/4)