Помогите! При каких значениях х имеет смысл??? Срочнл

2x+3x-50
 D=9-4*2*(-5)=49
  x=(-3+7)/4=1   x=(-3-7)/4=-2.5
    
                             -2.5                                  1
                 =======o------------------------------o=========gt;
                                       x(-;-2.5][1;+)

4x-12x+90
 D=(-12)-4*4*9=0
  x=12/8=1.5
                                                 1.5
                                 ========o============gt;
                                    x(-;+)