若a+b=7,ab=5,则(a-b)的二次方=要有算式
<p>问题：若a+b=7,ab=5,则(a-b)的二次方=要有算式<p>答案：↓↓↓<p class="nav-title mt10" style="border-top:1px solid #ccc;padding-top: 10px;">郭力培的回答：<div class="content-b">网友采纳 (a-b)² =a²-2ab+b² =a²+2ab+b²-4ab =(a+b)²-4ab =7²-4*5 =29
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