which following trinomial is a perfect square?

Question

A. x^2 + 2x - 3
B. x^2 - 4x - 4
C. x^2 + x + 1/4
D. x^2 - x -56

question B & C 1-term and 3-term is perfect square. how do figure which is perfect square?

Answer 1

automatically rule out A and D, last terms are not perfect squares
Also rule out B, since both front and back must be positive.

So it could only be C , if any at all.
take √ of both first and last, multiply those results, then double to get the middle term.
looks like C is it!
(x+1/2)^2 = x^2 + x + 1/4