计算(4x^2-2x^3+6x)/(-2x)-(x-1)^2y^2-4/y^2-y-6)+(y+2/y-3)/(y+1/y-3)

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计算(4x^2-2x^3+6x)/(-2x)-(x-1)^2y^2-4/y^2-y-6)+(y+2/y-3)/(y+1/y-3)
计算
(4x^2-2x^3+6x)/(-2x)-(x-1)^2
y^2-4/y^2-y-6)+(y+2/y-3)/(y+1/y-3)

计算(4x^2-2x^3+6x)/(-2x)-(x-1)^2y^2-4/y^2-y-6)+(y+2/y-3)/(y+1/y-3)
原式=-2x+x^2-3-x^2+2x-1
=-4
原式=(y+2)(y-2)/(y-3)(y+2)+(y+2)/(y+1)
=(y-2)/(y-3)+(y+2)/(y+1)
=(y^2-y-2+y^2-y-6)/(y-3)(y+1)
=(2y^2-2y-8)/(y-3)(y+1)

(4)(3x-4)(3x+4)=(9x2-16)
(5)2a-b3c=2a-(b3c);a-2b+c=a+(-2b+c)
余弦定理
a2=b2+c2-2bccosA
解出这个一元二次方程即可