Clear[K,a,b,c,d]
K=3
a=0
b=8
c=-5
d=5

Plot[Evaluate[u[x]/. NDSolve[{u''[x]-(x^2-K)*u[x] ==0,u[0]==0,u'[0]==1},u[x],{x,10^(-8),10},MaxSteps->1000]],{x,a,b},PlotRange->{c,d}]
