Write the formula for newton's method and use the given initial approximation to compute the approximations x_1 and x_2. f(x) = x^2 + 21, x_0 = -21 x_n + 1 = x_n - (x_n)^2 + 21/2(x_n) x_n + 1 = x_n - (x_n)^2 + 21 x_n + 1 = x_n - 2(x_n)/(x_n)^2 + 21 use the given initial approximation to compute the approximations x_1 and x_2. x_1 = (do not round until the final answer. then round to six decimal places as needed.)