We do completing the square as follows:
1. Put all terms with variable on one side and the constants on the other side.
5x^2 - 3x = 25
2. Factor out the coefficient of the x^2 term.
5(x^2 - 3x/5) = 25
3. Inside the parentheses, we add a number that would complete the square and also add this to the other side of the equation. In this case we add 9/100 and on the other side we add 9/20.
5(x^2 - 3x/5 + 9/100) = 25 + 9/20
4. We simplify as follows:
5(x^2 - 3x/5 + 9/100) = 25 + 9/20
5(x - 3/10)^2 = 509/20
(x - 3/10)^2 = 509/100
x1 = √(509) /100 + 3/10
x2 = -√(509) /100 + 3/10