Быстрее всего значение 
вычисляется по формуле Виета
Программа на python:
#(c) NaaMan
import math
def fnc1():
a,b = 1, -1
while True:
c = 1 / a
yield c
a = (abs(a) + 2) * b
b = -b
def fnc2():
a, b = 2, 1
while True:
c = a / b
yield c
if a > b:
b += 2
else:
a += 2
def fnc3():
a = 1
while True:
c = 1 / (a * a)
yield c
a += 1
def fnc4():
a = math.sqrt(2)
while True:
c = a / 2
yield c
a = math.sqrt(2 + a)
leibniz = fnc1( )
vallis = fnc2()
squares = fnc3()
viett = fnc4()
n = int( input( 'n = '))
s1 = 0
s2 = 1
s3 = 0
s4 = 1
while n:
s1 += next( leibniz)
s2 *= next( vallis)
s3 += next( squares)
s4 *= next( viett)
n -= 1
print( 'leibniz = ', s1 * 4)
print( 'vallis = ', s2 * 2)
print( 'squares = ', math.sqrt(s3 * 6))
print( 'viett = ', 2 / s4)
Результаты выполнения программы:
program proga;
var str: array of string;
readstr: string; i, x, err, count: integer;
necheti: array [1..3] of integer; y: boolean;
begin
y := false;
while y = false do begin;
Readln(readstr);
str := readstr.Split(' ');
for i := 1 to Length(str) do begin
Val(str[i - 1], x, err); if (x mod 2 <> 0) and (x < 0) then begin count += 1; if count = 1 then necheti[1] := x; if count = 2 then necheti[2] := x; if count = 3 then necheti[3] := x;
if count = 3 then begin Writeln('1: ', necheti[1]);
Writeln('2: ', necheti[2]);
Writeln('3: ', necheti[3]); y := true; end;
end;
end;
end;
end.
Объяснение:
Вводить значения строго через пробел и без запятых
ax(x-bx)+c=0
ax+c=o
x=0 x-bx=0