[latex]1);frac{8a-3b+2ab-12}{4+b+4a+ab}=frac{2a(4+b)-3(b+4)}{(4+b)+a(4+b)}=frac{(2a-3)(b+4)}{(a+1)(b+4)}=frac{2a-3}{a+1}[/latex] [latex]2);frac{3,25cdot4,28-1,15cdot5,22+3,25cdot5,22-1,15cdot4,28}{11,6^2-7,4^2}=\ =frac{3,25(4,28+5,22)-1,15(5,22+4,28)}{(11,6-7,4)(11,6+7,4)}=frac{(3,25-1,15)(5,22+4,28)}{(11,6-7,4)(11,6+7,4)}=\ =frac{2,1cdot9,5}{4,2cdot19}=frac{2,1cdot9,5}{2cdot2,1cdot2cdot9,5}=frac14=0,25[/latex]