(2X-Y)(Y+2X)-(2y+X)(-2y-x)
=(2X-Y)(Y+2X)+(2y+X)(x+2y)
=4x²-y²+(x+2y)²
=4x²-y²+x²+4xy+4y²
=5x²+4xy+3y²
代人x=1,y=2
原式=(2X-Y)(Y+2X)-(2y+X)(-2y-x)
=5x²+4xy+3y²
=5×1²+4×1×2+3×2²
=25
(2X-Y)(Y+2X)-(2y+X)(-2y-x)
=(2X-Y)(Y+2X)+(2y+X)(x+2y)
=4x²-y²+(x+2y)²
=4x²-y²+x²+4xy+4y²
=5x²+4xy+3y²
代人x=1,y=2
原式=(2X-Y)(Y+2X)-(2y+X)(-2y-x)
=5x²+4xy+3y²
=5×1²+4×1×2+3×2²
=25