Suppose that Newton's method is used to locate a root of the equation f(x) = 0 with initial approximation x₁ = 5. If the second approximation is found to be x₂ = 1, and the tangent line to f(x) at x = 5 passes through the point (20,4), find f(5).

Use Newton's method with initial approximation x1= 7 to find x2, the second approximation to the root of the equation x3 = 8x 1.