题干
阅读理解.
因为 (a+
)2 =a2 +2a⋅
+(
)2 =a2 +
+2 ， ①
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因为 (a−
)2 =a2 −2a⋅
+(
)2 =a2 +
−2 ②
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所以由①得： a2 +
=(a+
)2 −2 ， 由②得： a2 +
=(a−
)2 +2
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所以 a4 +
=(a2 +
)2 −2
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试根据上面公式的变形解答下列问题：
