3.5²+60×3.5×1.5+1.5²
=3.5²+2×3.5×1.5+1.5²+58×3.5×1.5
=(3.5+1.5)²+58×3.5×1.5
=25+58×3.5×1.5
=25+29×7×1.5
=25+(30-1)×10.5
=25+30×10.5-1×10.5
=25+315-10.5
=340-10.5
=329.5
=3(25*2.6^2-4*3.5^2)
=3(5*2.6-2*3.5)(5*2.6+2*3.5)
=3*6*20
=360
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