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You need to insert more parentheses. For example, it is not clear where the denominator ends in q / 4 ∏ ε_{0}|r - r_{0}|^{3}(r - r_{0}). This should be written as (q / (4 ∏ ε_{0}|r - r_{0}|^{3})) (r - r_{0}). Similarly, √-1a^{2}+1a^{2}+1a^{2}can be written as sqrt(-1a^{2}+1a^{2}+1a^{2}).