Condition 1: If x = 1, y = 1, z =0; sufficient to prove x^4 + y^4 > z^4. If x = 4, y = 4, z = 5; insufficient to prove x^4 + y^4 > z^4. Therefore condition 1 is insufficient.
Condition 2: If x = 1, y = 1, z = 0; sufficient to prove x^4 + y^4 > z^4. If x = 1, y = 1, z = -3; insufficient to prove x^4 + y^4 > z^4. Therefore condition 2 is in sufficient.
Combining 1 and 2: If x = 1, y = 1, z = 0; sufficient to prove x^4 + y^4 > z^4. If x = 4, y = 4, z = -5; insufficient to prove x^4 + y^4 > z^4. Therefore conditions 1 and 2 are not sufficient.作者: youngerlee 时间: 2011-1-6 06:47
明白了。谢谢##
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