(2x-y-3)(2x-y+3)-(2x-y-3)^2 已知a-1/2=2,求a^2+1/a^2,a^4+1/a^4的值

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(2x-y-3)(2x-y+3)-(2x-y-3)^2 已知a-1/2=2,求a^2+1/a^2,a^4+1/a^4的值
(2x-y-3)(2x-y+3)-(2x-y-3)^2 已知a-1/2=2,求a^2+1/a^2,a^4+1/a^4的值

(2x-y-3)(2x-y+3)-(2x-y-3)^2 已知a-1/2=2,求a^2+1/a^2,a^4+1/a^4的值
(2x-y-3)(2x-y+3)-(2x-y-3)^2
=(2x-y-3)[(2x-y+3)-(2x-y-3)]
=(2x-y-3)(2x-y+3-2x+y+3)
=6(2x-y-3)
a-1/a=2?
a^2+1/a^2
=(a-1/a)²+2
=(2)²+2
=6,
a^4+1/a^4
=(a²+1/a²)²-2
=6²-2
=34.