x^2-28x What number must you add to the polynomial below to complete the square? Please show steps ! Please ! Thanks

Question

anonymous · Answer

lets say you add b
to make it some (x-a)^2
then

x^2 - 28x +b = (x-a)^2
x^2 -28x + b= x^2 -2ax + a^2

Now compare coefficients

-28=-2a
and
b=a^2
so
a=14
b=196

anonymous · Answer

So which number would I add to complete the square ? Also I think your solving for a and b . i just need to know what number makes this equation a perfect square binomial.

anonymous · Answer

didnt i mention that you add b?

anonymous · Answer

196 right ?

anonymous · Answer

right