Is x4 + y4 > z4 ?
(1) x2 + y2 > z2
(2) x + y > z
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
条件一:x^2+y^2>z^2,可知不等式两边都大于0,将两边同时平方,不等号的方向不变。得到:x^4+y^4+2(x^2)(y^2)>z^4,因为2(x^2)(y^2)是大于0的,所以条件一不能推出x^4+y^4>z^4
举例子:6,8,9
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