The object makes a uniform deceleration linear motion with initial velocity of 6 m / s and acceleration of - 1 m / s, and the displacement of the object passing through in a few seconds is 0.5 m?

The object makes a uniform deceleration linear motion with initial velocity of 6 m / s and acceleration of - 1 m / s, and the displacement of the object passing through in a few seconds is 0.5 m?

5 = 6t-1 * (the square of T) can solve the value of T. I don't have a calculator at the moment, so it's not convenient to calculate