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解答

(x+2)(x+12)(x+4)(x+6)+3x^2
=(x^2+14x+24)(x^2+10x+24)+3x^2

令x^2+24=y
(14x+y)(10x+y)+3x^2=143x^2+24xy+y^2
十字交乘得(11x+y)(13x+y)
再把y代回得(x^2+11x+24)(x^2+13x+24)
答:B

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