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電子課本網(wǎng) › 第28頁

第28頁

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$解：原式?=[(a+b)(a-b)]2?$

$? =(a2-b2)2?$

$? = a^4-2a2b2+b^4?$

$解：原式?=(a+b)2-32?$

$? =a2+2ab+b2-9?$

$解：?(1)x^2+y^2?$

$?=x2+y2+2xy-2xy?$

$? =(x+y)2-2xy?$

$? =32-2?$

$? =7?$

$? (2)?原式?=x2+y2-xy?$

$? =7-1?$

$? =6?$

?$(3)$?原式?$=x2+y2-2xy$?

?$ =7-2$?

?$ =5$?

??$ x2-xy+\frac 14y2$??

$??-8ab??$

$??±28??$