Will give brainliest to correct answer.

Use Pythagorean's Theorem to solve for c.  .  We will simplify the right side by squaring both terms.    which simplifies even further to  .  In that polynomial, the leading coefficient, 4, is a perfect square, and so is the constant at the end, 9.  So that polynomial is the sum of perfect squares.  It will break down like this:    so then taking the square root of both sides gives us that c = 2x + 3, choice on the top right.