Complete the square

Question

Fill in the number that makes the polynomial a perfect square quadratic

y^2+28y+__?

Answer 1

When you have the form

y² + by,

you complete the square by adding b²/4

b = 28

b²/4 = 28²/4 = 196

With the square completed, the polynomial is

y² + 28y + 196 = (y + 14)²