括号a+b+c乘以括号a-b-c等于多少?.
括号a+b+c乘以括号a-b-c等于多少?
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(a+b+c)*(a-b-c)
=[(a+(b+c)]*[a-(b+c)]
=a²-(b+c)²
=a²-b²-c²-2bc