(x+2y)(x-2y)+(9x的三次方×y-12

(x+2y)(x-2y)+(9x的三次方×y-12xy的三次方)÷(-3xy) 化简求值其中x=1 y=-2

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(x+2y)(x-2y)+(9x的三次方×y-12xy的三次方)÷(-3xy)
=(x+2y)(x-2y)+3xy(3x²-4y²)÷(-3xy)
=x²-4y²-3x²+4y²
=-2x²
=-2