[tex]\displaystyle\bf\\a_{1} =1,2\\\\d=-0,1\\\\a_{2} =a_{1}+d=1,2-0,1=1,1\\\\a_{3} =a_{2} +d=1,1-0,1=1\\\\a_{4} =a_{3} +d=1-0,1=0,9\\\\Otvet \ : \ 1,2 \ \ ; \ \ 1,1 \ \ ; \ \ 1 \ \ ; \ \ 0,9[/tex]