当x=2,y=1/2时,求代数式(x+y)(x-Y)+(x-y)的2次方 -x(x-3y) 5
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(x+y)(x-Y)+(x-y)的2次方 -x(x-3y)
=(x-y)(x+y+x-y)-x(x-3y)
=2x(x-y)-x(x-3y)
=x(2x-2y-x+3y)
=x(x+y)
=2(2+1/2)
=5
=(x-y)(x+y+x-y)-x(x-3y)
=2x(x-y)-x(x-3y)
=x(2x-2y-x+3y)
=x(x+y)
=2(2+1/2)
=5
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展开全部
当x=2,y=1/2时,求代数式(x+y)(x-Y)+(x-y)的2次方 -x(x-3y)
解;(x+y)(x-Y)+(x-y)的2次方 -x(x-3y)
=(x-y)(x+y+x-y)-x(x-3y)
=2x(x-y)-x(x-3y)
=x(2x-2y-x+3y)
=x(x+y)
=2(2+1/2)
=5
解;(x+y)(x-Y)+(x-y)的2次方 -x(x-3y)
=(x-y)(x+y+x-y)-x(x-3y)
=2x(x-y)-x(x-3y)
=x(2x-2y-x+3y)
=x(x+y)
=2(2+1/2)
=5
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