Сократите дробь: у^2+y ---------; y^2 a^2-2a ----------; a^2-4
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(y^2+y)/ y^2=y(y+1)/y^2=(y+1)/y (a^2-2a)/(a^2-4)= a(a-2)/(a-2)(a+2)=a/(a+2)