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1) x²-9-x²-6x-9=-6x-18=-6(x+3)
należy wykorzystać dwa wzory skróconego mnożenia:
(a-b)(a+b)=a²-b²
(a+b)²=a²+2ab+b²
czyli:
(x-3)(x+3)-(x+3)²=x²-9-(x²+2*x*3+3²)=x²-9-(x²+6x+9)=x²-9-x²-6x-9=
=-6x-18