Question 136313
if equation is:
sqrt (T + 12) - T = 0  (eq 1)
then you did it well and
T^2-T-12=0  (eq 2)
T=4 and T=-3

but solutions of the (eq 1) are included in solutions of (eq 2)
(-3 is a solution of the eq 2 but not a solution of eq 1)

Answer: T=4