разложите на множители: 4х^2y^2-9a^4=(2xy-3a^2)(2xy+3a^2)
25a^2-(a+3)^2=(5a-a-3)(5a+a+3)=(4a-3)(6a+3)=3(4a-3)(2a+1)
27m^3+n^3=(3m+n)(9m^2-3mn+n^2)
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