Plot[{x^2,-x^2,x^2Cos[6*Pi*x]},{x,-1.5,1.5},PlotRange->{-2,2}]

Plot[Sin[x]/x,{x,-15,15},PlotRange->{-.5,1.5}]

Plot[Sin[50x],{x,-10,10},PlotRange->{-1.5,1.5}]

Manipulate[Plot[a*Sin[k( x-b)],{x,-Pi,Pi},PlotRange->{-1,1}],{a,-1,1},{k,.1,10},{b,0,10}]