9 х2 - 12 х + 40 = 0

3 х2 + 7 х + 5 = 0

х2 - 12 х + 45 = 0

9 х2 - 12 х + 40 = 0

D = b^2 - 4ac = (-12) ^2 - 4*9*40 = 144 - 1440 = - 1269

D<0 - net kornej

3 х2 + 7 х + 5 = 0

D = b^2 - 4ac = 7^2 - 4*3*5 = 49-60=-11

D<) - net kornej

х2 - 12 х + 45 = 0

D = (-12) ^2 - 4*1*45 = 144 - 180 - - 36

D<0 - net kornej