The teacher will be very surprised to see your correct solution 😉
3 __________
-x / 2
------------- + 2*x*\/ 144 - x = 0
__________
/ 2
\/ 144 - x
sum
___ ___ - 4*\/ 6 + 4*\/ 6
=
0
product
___ ___ 0*-4*\/ 6 *4*\/ 6
=
0
0
x1 = 0
___ x2 = -4*\/ 6
___ x3 = 4*\/ 6
x3 = 4*sqrt(6)