Answer:
A (361)
Step-by-step explanation:
A "perfect square trinomial" has the form
ax^2 + 2ab + b^2. If a happens to be 1, which it is in the given x^2 − 19x + c, then 2(1)(b) = - 19. Solving for b, we get b = -19/2.
Then b^2 in the general "perfect square trinomial" is the same as c: (-19/2)^2, or 90.25, or 90 1/4, or 361/4/
Choosing A (361) makes the given expression a perfect square trinomial.
