What number can we place in the box to make the quadratic below the square of a binomial? \[ x^2 + \dfrac{5}{3}x + \boxed{\phantom{000}} \]
x2 + 5/3 x + ? Use 'completing the square ' method
take 1/2 of 5/3 = 5/6 and square it 25/36
x^2 + 5/3 x + 25/36 = (x + 5/6)2