$$a^{2}$$ - $$b^{2}$$=21.$$a^{4}$$ - $$b^{4}$$=?
1：a+b=-3
2：a-b=7
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AStatement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
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BStatement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
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CBoth statements TOGETHER are sufficient, but NEITHER one ALONE is sufficient.
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DEACH statement ALONE is sufficient.
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EStatements (1) and (2) TOGETHER are NOT sufficient.
显示答案
正确答案: D