用简便方法计算:21.5^2-3*21.5+1.5^2-100
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用简便方法计算:21.5^2-3*21.5+1.5^2-100
用简便方法计算:21.5^2-3*21.5+1.5^2-100
用简便方法计算:21.5^2-3*21.5+1.5^2-100
21.5^2-3*21.5+1.5^2-100
=21.5*21.5-3*21.5+1.5^2-100
=(21.5-3)*21.5+1.5^2-100
=18.5*21.5+1.5^2-100
=18.5*(20+1.5)+1.5^2-100
=18.5*20+18.5*1.5+1.5*1.5-100
=18.5*20+(18.5+1.5)*1.5-100
=18.5*20+1.5*20-100
=(18.5+1.5)*20-100
=400-100
=300