Jawabanmu

2014-09-04T22:04:46+07:00
(2x-y)(x+2y)-(-x²+2xy+y²)
= (2x^2+4xy-xy-2y^2) -(-x^2+2xy+y^2)
=(2x^2-(-x^2))+3xy-2xy)+(-2y^2-y^2
=3x^2+xy-3y^2
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2014-09-04T22:06:58+07:00
2x^2+3xy-2y^2+x^2-2xy-y^2=3x^2+xy-3y^2
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