已知y-x=2,x-3y=1,则x2-4xy+3y2的值为( )A.-1B.-2C.-3D.-4
题型:单选题难度:一般来源:不详
已知y-x=2,x-3y=1,则x2-4xy+3y2的值为( ) |
答案
x2-4xy+3y2=(x-3y)(x-y), ∵y-x=2,x-3y=1, ∴x2-4xy+3y2=1×(-2)=-2. 故选B. |
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