若x+y=7,xy=12,则x²-3xy+y²= ( )
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![若x+y=7,xy=12,则x²-3xy+y²= ( )](/uploads/image/z/9301492-28-2.jpg?t=%E8%8B%A5x%2By%3D7%2Cxy%3D12%2C%E5%88%99x%26%23178%3B-3xy%2By%26%23178%3B%3D+%EF%BC%88+%EF%BC%89)
若x+y=7,xy=12,则x²-3xy+y²= ( )
若x+y=7,xy=12,则x²-3xy+y²= ( )
若x+y=7,xy=12,则x²-3xy+y²= ( )
x²-3xy+y²
=x²+2xy+y²-5xy
=(x+y)²-5xy
=7²-5*12
=49-60
=-11
若x+y=7,xy=12,则x²-3xy+y²= (-11 )
-11