No. Because sometimes, there are equations like "3x^2-2x+5" which when you simplify it, it is not a perfect square. You can determine if a trinomial is a perfect square by these steps.
(a) the middle sign can be + or -, but the third sign should be +
(b) the middle coefficient is twice the square root of the first coefficient times the square root of the third coefficient
a² + 14a + 49 => signs are fine, and 14 = 2*√1*√49 => (a+7)²
9z² - 3z + 1 => signs are fine, but 3 ≠ 2*√9*√1