The false position method

The false position method

False place method


The False Position method in Numeric Analysis is a method to happen the root which involves thoughts of both Bisection and Secant method.

Diagrammatic Explanation

  • In this diagram which is shown above the ruddy curve shows the map degree Fahrenheit ( x ) and the bluish lines are the secants.
  • Merely like the instance of Bisection method, in the false place method besides we start with two points a0 and b0 such that degree Fahrenheit ( a0 ) and f ( b0 ) are of opposite marks, which implies by the intermediate value theorem that the map degree Fahrenheit has a root in the interval [ a0, b0 ] .
  • The expression used above is besides used in the secant method, but the secant method ever retains the last two computed points, while the false place method retains two points which surely bracket a root.
  • The lone difference between the false place method and the bisection method is that the latter utilizations cn = ( an + bn ) / 2.


  • If the initial end-points a0 and b0 are chosen such that degree Fahrenheit ( a0 ) and f ( b0 ) are of opposite marks, so one of the end-points will meet to a root of degree Fahrenheit.
  • Asymptotically, the other end-point will stay fixed for all subsequent loops while the meeting end point becomes updated.
  • As a consequence, unlike the bisection method, the breadth of the bracket does non be given to zero. As a effect, the additive estimate to f ( ten ) , which is used to pick the false place, does non better in its quality.

Newton ‘s method


  • In the 19th cent. Two celebrated scientists viz. Issac Newton and Joseph Raphson jointly made a method of happening roots of a equation called Newton-Raphson method.
  • This method is till now the best known method for happening in turn better estimates to the nothings ( or roots ) of a map in the topic of Numeric Analysis.
  • Correct executions of this method embed it in a modus operandi that besides detects and possibly overcomes possible convergence failures.
  • Interestingly, it can be deduced that an alternate application of Newton-Raphson division, is to rapidly happen the reciprocal of a figure utilizing lone generation and minus.

Diagrammatic Justification

  • Here we have show an illustration of one loop of Newton ‘s method ( the map ? is shown in blue and the tangent line is in ruddy ) . In this instance xn+1 is a better estimate than xn for the root ten of the map degree Fahrenheit.
  • The thought of the method is as follows: one starts with an initial conjecture which is moderately close to the true root, so the map is approximated by its tangent line ( which can be computed utilizing the tools of concretion ) , and one computes the x-intercept of this tangent line ( which is easy done with simple algebra ) .
  • This x-intercept will typically be a better estimate to the map ‘s root than the original conjecture, and the method can be iterated.
  • The procedure is started off with some arbitrary initial value x0. ( The closer to the nothing, the better. But, in the absence of any intuition about where the nothing might lie, a “ hit and test ” method might contract the possibilities to a moderately little interval by appealing to the intermediate value theorem. )
  • The method will normally meet, provided this initial conjecture is near adequate to the unknown nothing, and that ? ‘ ( x0 ) ? 0.
  • Furthermore, for a nothing of multiplicity1, the convergence is at least quadratic ( see rate of convergence ) in a vicinity of the nothing, which intuitively means that the figure of right figures approximately at least doubles in every measure.


The root happening methods discussed in this subdivision are rather successful for ciphering roots of any given equation. The False Position Method is utile for happening the existent roots of an equation. The Newton Raphson ‘s method nevertheless can be used to cipher both existent and complex roots. Newton Raphson ‘s method is utile in instances when the map degree Fahrenheit ( x ) graph is about perpendicular while traversing the x-axis.