(2a+3b)²+(3a-b)²=4a²+12ab+9b²+9a²-6ab+b²=13a²+6ab+10b².a=1/2,b=-1/2即a=-b=1/2a=-b时,(2a+3b)²+(3a-b)²=13a²+6ab+10b²=13a²-6a²+10a
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