Сделать рисунок параболы более гладким

void __fastcall TForm1::Button1Click(TObject *Sender)
{
//os x
Image1->Canvas->MoveTo(20,Image1->Height/2);
Image1->Canvas->LineTo(Image1->Width-20,Image1->Height/2);
Image1->Canvas->LineTo(Image1->Width-20-5,Image1->Height/2-5);
Image1->Canvas->LineTo(Image1->Width-20,Image1->Height/2);
Image1->Canvas->LineTo(Image1->Width-20-5,Image1->Height/2+6);
 
//tick x
for (int i=Image1->Width/2; i<Image1->Width-30; i+=20){
     Image1->Canvas->MoveTo(i,Image1->Height/2-3);
     Image1->Canvas->LineTo(i,Image1->Height/2+3);
     }
for (int i=Image1->Width/2; i>30; i-=20){
     Image1->Canvas->MoveTo(i,Image1->Height/2-3);
     Image1->Canvas->LineTo(i,Image1->Height/2+3);
     }
 
//os y
Image1->Canvas->MoveTo(Image1->Width/2,Image1->Height-20);
Image1->Canvas->LineTo(Image1->Width/2,20);
Image1->Canvas->LineTo(Image1->Width/2-5,20+5);
Image1->Canvas->LineTo(Image1->Width/2,20);
Image1->Canvas->LineTo(Image1->Width/2+6,20+6);
 
//tick y
for (int i=Image1->Height/2; i<Image1->Height-30; i+=20){
     Image1->Canvas->MoveTo(Image1->Width/2-3,i);
     Image1->Canvas->LineTo(Image1->Width/2+3,i);
     }
for (int i=Image1->Height/2; i>30; i-=20){
     Image1->Canvas->MoveTo(Image1->Width/2-3,i);
     Image1->Canvas->LineTo(Image1->Width/2+3,i);
     }
 
//график
 
int y = -1;
int x = -1;
 
 
Image1->Canvas->Pen->Width = 2;
      for (x=-100; x<100; x++){
             y=x*x;
              if (x==-100)
 
               Image1->Canvas->MoveTo(x*20+Image1->Width/2,-y*20+Image1->Height/2);
               Image1->Canvas->LineTo(x*20+Image1->Width/2,-y*20+Image1->Height/2);
     }
Image1->Canvas->Pen->Width = 1;
 
 
 
}

//график
 
int y = 10000;
int x = -100;
 
Image1->Canvas->Pen->Width = 3;
Image1->Canvas->MoveTo(x+Image1->Width/2,-y/20+Image1->Height/2);
for (x=-100; x<100; x++){
    y=x*x;
    Image1->Canvas->LineTo(x+Image1->Width/2,-y/20+Image1->Height/2);
    }
Image1->Canvas->Pen->Width = 1;