Brainlies ! write x^2 − 2x − 3 = 0 in the form (x − a)^2 = b, where a and b are integers. (x − 4)^2 = 3 (x − 3)^2 = 2 (x − 2)^2 = 1 (x − 1)^2 = 4

When the quadratic expression is x^2 +ax + ..., the binomial square will be
.. (x +(a/2)^2

You have a=-2, so the binomial square will be of the form (x -1)^2. You don't even need to work out the rest of it to know that ...
.. the 4th selection is appropriate.