f(x) = 0.5x -4

a)  05.x -4 = -5

     0,5х = -1

     х = - 2

б)    0,5х -4 = 0                                               в)     0,5х -4 = 2,5

        0,5х = 4                                                             0,5х = 6,5 

        х = 8                                                                  х = 13