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题库 / Prep2007E2-DS-188
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.
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1）x^2+y^2和z^2都是正数
（x^2+y^2)^2=x^4+y^4+2x^2y^2>z^4，但不能推出x^4+y^4>z^4
2)x,y，z的符号不确定，不能判断
1）+2）只能知道x^4+2x^2y^2+y^4>z^4,不能判断x^4+y^4与z^4的大小
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