Could not compile used unit 问题
unit MySubs;

interface

uses
Math, Graphics;
type
function Power10N(n:INteger):Integer; //计算10的n次方
function StandReal(x:Real;n:Integer):Real; //计算时数保留n位小数的转换结果
procedure PaintG(PCanvas:TCanvas;a,b,c:Integer); //在画布上画出一元二次方程的图形
end;

implementation

function Power10N(n:INteger):Integer;
var
i:Integer;
Result:=1;
for i:=1 to n do
Result:=Result*10;
end;

function StandReal(x:Real;n:Integer):Real;
begin
Result:=Trunc(Abs(x)*Power10N(n)+0.5)/Power10N(n)*Sign(x);
end;

procedure PaintG(PCanvas:TCanvas;a,b,c:Integer);
var
x,y,first:Integer;
begin
PCanvas.Pen.Color:=clRed; //用红色画坐标线和坐标值
PCanvas.MoveTo(10,210);
PCanvas.LineTo(410,210);
PCanvas.MoveTo(210,10);
PCanvas.LineTo(210,410);
PCanvas.TextOut(220,10,'200');
PCanvas.TextOut(220,400,'-200');
PCanvas.TextOut(10,220,'-50');
PCanvas.TextOut(400,220,'50');
PCanvas.Pen.Color:=clBlue; //用蓝线画函数曲线
first:=0;
for x:=-50 to 50 do begin
y:=a*Sqr(x)+b*x+c;
if Abs(y)<200 then
first:=first+1;
else
first:=0;
if first=1 then
PCanvas.MoveTo(4*x+210,210-y);
if first=1 then
PCanvas.LineTo(4*x+210,210-y);
end;
end;
end.


[解决办法]
type
...
end;

1.type和end去掉

var
i:Integer;
begin
Result:=1;

2.少了begin

if Abs(y)<200 then
first:=first+1;
else
first:=0;

3.分去掉

[解决办法]
把btnProject.SetFocus注释掉试试？