计算下列各题(2x-y)(2x+y)+(y-x)(2x-5y)(3×10^-3)^4×(-2×10^2)^3[(x^2-

(2x-y)(2x+y)+(y-x)(2x-5y)
=4x²-y²+2xy-5y²-2x²+5xy
=2x²+7xy-6y²
(3×10^-3)^4×(-2×10^2)^3
=81×10^-12 ×(-8×10^6)
=-648×10^(-6)
=-6.48×10^(-4)
[(x^2-4)/(x^2-x-6)+(x+2)/(x-3)]÷(x+1)/(x-3)
=[(x+2)(x-2)/(x-3)(x+2) +(x+2)/(x-3)] ×(x-3)/(x+1)
=[(x-2)/(x-3)+(x+2)/(x-3)] ×(x-3)/(x+1)
=2x/(x-3) ×(x-3)/(x+1)
=2x/(x+1)
(-a^-2/b)^-2(-b^2/a)÷(1/ab)^-4
=b²/a^4 ×(-b²/a)×1/a^4b^4
=-1/a^9