@engr-ali said in replace the part of curve between the points:

AoA, Sir if you may plz explain “replace the part of curve between the points A(x_n, f(x_n)) and B(x_n-1, f(x_n-1)) by a chord in the interval” . diagrammatic explanation will be a great help in comprehension of the subject matter. Thanks

A chord is basically a straight line by joining two points of a curve or circle. The root of a equation means that when we give input value x then the functional value of that input will be zero then x is called the root of that equation. We take the two points of the interval on the chord instead of the curve shape because the value of root lies in that interval and this mean this value will lie on x-axis and if this is the root then functional value will be zero and we know that y-axis (functional value) is zero at x-axis.