The number needed to complete the square is 9/4
Given the expression x^2 + 3x + ?
Using the completing the square;
Step 2: Get the coefficient of x
The coefficient of x is 3
Step 3: Get the half of coefficient of x
Hale of the coefficient = 3/2
Step 4: Take the square of the result
Square of the result = ()3/2)^2 = 9/4
Hence the number needed to complete the square is 9/4
Learn more on completing the square here: https://brainly.com/question/1596209