Câu 2:
Uses crt;
Var i, n: integer;
S: real;
Begin
Clrscr;
Write('Nhap n = '); readln(n);
s:=0;
For i:=1 to n do s:=s+1/sqr(i);
Writeln('Tong = ',s:8:2);
Readln
End.
Câu 4:
Uses crt;
Var a, b, x: real;
Begin
Clrscr;
Write('Nhap a = '); readln(a);
Write('Nhap b = '); readln(b);
If a <> 0 then writeln('Nghiem la: x = ',-b/a:2:2)
Else if b = 0 then writeln('PT co vo so nghiem')
Else writeln('PT co vo nghiem');
Readln
End.
