Fill in the blank with a constant, so that the resulting quadratic is the square of a binomial. \(x^2 + \dfrac{4}{5}x + \underline{~~~~}\)
Completing the square, we get (x + 4/5)^2 = x^2 + 4/5*x = 16/25, so the number 16/25 should go in the blank.
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