if else construction

There are several errors in your code. And you should use a cond when dealing with multiple conditions (think of it as a series of IF/ELSE IF/…/ELSE statements).

Be aware that the expression (and (> x 1) (= x 1)) will never be true, as x is either greater than or equal to 1, both conditions can never be true at the same time. You probably meant (or (> x 1) (= x 1)), but even so that expression can be written more concisely as (>= x 1). The same considerations apply for the condition (and (< x 2) (= x 2)).

I believe this is what you were aiming for:

(define (equation x)
  (cond ((> x 2)
         (+ (- (* x x) x) 4))
        ((and (>= x 1) (<= x 2))
         (/ 1 x))
        (else 0)))

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