9х2 - 12х + 40 = 0
3х2 + 7х + 5 = 0
х2 - 12х + 45= 0 

9х2 - 12х + 40 = 0D = b^2 - 4ac = (-12)^2 - 4*9*40 = 144 - 1440= -1269D<0 - net kornej3х2 + 7х + 5 = 0D = b^2 - 4ac = 7^2 - 4*3*5 = 49-60=-11D<) - net kornejх2 - 12х + 45= 0 D = (-12)^2 - 4*1*45 = 144 - 180 - -36D<0 - net kornej