已知x-y=5,xy=3,则3xy-7x+7y=?

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已知x-y=5,xy=3,则3xy-7x+7y=?已知x-y=5,xy=3,则3xy-7x+7y=?已知x-y=5,xy=3,则3xy-7x+7y=?x-y=5y-x=-53xy-7x+7y=9+7×

已知x-y=5,xy=3,则3xy-7x+7y=?
已知x-y=5,xy=3,则3xy-7x+7y=?

已知x-y=5,xy=3,则3xy-7x+7y=?
x-y=5
y-x=-5
3xy-7x+7y=9+7×-5
=-26

-26

3xy-7x+7y
=3xy-7(x-y)
=3*3-7*5
=9-35
=-26

3xy-7x+7y=3xy-7(x-y)=3*3-7*5=-26

3xy-7x+7y=?
=3xy-7(x-y)
=3*3-7*5
=9-35
=-26

-26

因为:x-y=5,xy=3
所以:3xy-7x+7y=3xy-7(x-y)=3×3-7×3=﹣12

3xy-7x+7y=3xy-7(x-y)=3x3-7x5=9-35=-26

3xy-7x+7y=3xy-7(x-y)=3*3-7*5=-26