(x+y)四次方-18(x+y)平方+81

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(x+y)四次方-18(x+y)平方+81(x+y)四次方-18(x+y)平方+81(x+y)四次方-18(x+y)平方+81(x+y)⁴-18(x+y)²+81=[(x+y)&

(x+y)四次方-18(x+y)平方+81
(x+y)四次方-18(x+y)平方+81

(x+y)四次方-18(x+y)平方+81
(x+y)⁴-18(x+y)²+81
=[(x+y)²-9]²
=(x²+2xy+y²-9)²

(x+y)四次方-18(x+y)平方+81
=[(x+y)二次方-9]平方
=(x+y+3)平方(x+y-3)平方

(x+y)四次方-18(x+y)平方+81
=[(x+y)²-9]
=(x+y-3)²(x+y+3)²

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(x+y)^4-18(x+y)^2+81
=[(x+y)^2]^2-2*9*(x+y)^2+9^2
=[(x+y)^2-9]^2
=[(x+y+3)*(x+y-3)]^2