Which method can't you use to solve this problem? x^2-47=0a.) factoring b.) squarerootsc.) quadratic formula

I️ dislike this question because all 3 methods could be used to solve. Although there are no rational factors, this equation can obviously be rewritten as a difference of squares as (x + sqrt(47))(x-sqrt(47)). A square root could be used by adding 47 to both sides and taking the square root. The quadratic formula can clearly be used as well. The result for each of these methods is that x = +-sqrt(47), which is the correct answer.