已知x-2y=3,则1/2x²-2xy+2y²的值是
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已知x-2y=3,则1/2x²-2xy+2y²的值是
已知x-2y=3,则1/2x²-2xy+2y²的值是
已知x-2y=3,则1/2x²-2xy+2y²的值是
1/2x²-2xy+2y²
=1/2(x²-4xy+4y²)
=1/2(x-2y)²
=1/2*3²
=9/2
1/2x²-2xy+2y²
=1/2(x²-4xy+4y²)
=1/2(x-2y)²
=1/2x3²
=1/2x9
=9/2
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由x-2y=3得2y-x=-3
∴原式=1/2x²-xy-xy+2y²
=1/2x²-xy+2y²-xy
=1/2x(x-2y)+y(x-2y)
=3/2x-3y
=3(1/2x-y...
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由x-2y=3得2y-x=-3
∴原式=1/2x²-xy-xy+2y²
=1/2x²-xy+2y²-xy
=1/2x(x-2y)+y(x-2y)
=3/2x-3y
=3(1/2x-y)
=3(x-2y)
=3X3
=9
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