计算：(1)x³∕x²•x^4 (2)-x²(x²-x+2)

(1)x³∕x²•x^4
=x³*x²
=x^5
(2)-x²(x²-x+2)
=-x^4+x³-2x²
(3)(-2a-3b)(-2a+3b)
=（-2a）²-(3b)²
=4a²-9b²
(4)(x-2)(x+1)-(x-1)²
=x²-x-2-x²+2x-1
=x-3
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