已知x+y=xy=4 求x^2+^2 x^4+x^4 x^8+y^8的值后面是三个式子x^2+x^2=?x^4+y^4=?x^8+_数学解答

已知x+y=xy=4 求x^2+^2 x^4+x^4 x^8+y^8的值
后面是三个式子
x^2+x^2=?
x^4+y^4=?
x^8+y^8=?

人气：362 ℃　时间：2020-09-29 05:14:34

解答

x²+y²
=(x+y)²-2xy
=4²-2×4
=8
x^4+y^4
=(x²+y²)²-2x²y²
=8²-2×4²
=32
x^8+y^8
=(x^4+y^4)²-2x^4y^4
=32²-2×256
=1024-512
=512