Exercise 2.34.  Evaluating a polynomial in x at a given value of x can 
be formulated as an accumulation. We evaluate the polynomial

using a well-known algorithm called Horner's rule, which structures the 
computation as

In other words, we start with an, multiply by x, add an-1, multiply by 
x, and so on, until we reach a0.  Fill in the following template to 
produce a procedure that evaluates a polynomial using Horner's rule. 
Assume that the coefficients of the polynomial are arranged in a 
sequence, from a0 through an.

(define (horner-eval x coefficient-sequence)
  (accumulate (lambda (this-coeff higher-terms) <??>)
              0
              coefficient-sequence))

For example, to compute 1 + 3x + 5x3 + x5 at x = 2 you would evaluate

(horner-eval 2 (list 1 3 0 5 0 1))

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(define (horner-eval x coefficient-sequence)
  (accumulate (lambda (this-coeff higher-terms) (* x (+ this-coeff higher-terms)))
              0
              coefficient-sequence))

also wrong, should be:

(+ this-coeff (* x higher-terms))