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The Newton-Raphson method is another way for solving an equation of the form

f(x)=0

Suppose α is a solution to this equation, and x0 is a number we believe to be close to α. The image below shows how the Newton-Raphson method works:

The idea is:

  • We guess an x0 and find the point (x0,y0) on the curve

  • We find the equation of the tangent to the curve at (x0,y0)

  • Then x1 is given by the point where this tangent crosses the x axis

Now, that process is a little long-winded. Using algebra, we can show that

x1=x0−f(x0)f′(x0)

This can be done again and again to get closer and closer to α. Generally,

xn+1=xn−f(xn)f′(xn)

Use the Newton-Raphson method, with a starting value of x0=1.1 to find 2 further approximations for one of the solutions to

2x2+3x−6=0