The answer is a² + 6. "Sum of a squared and 6" means you square a value and then add 6 to it.
T = 5 a
i = 4% aa
j = 1200
c = ...
j = cit/100
c = 100j / it
c = 100*1200 / 4*5
c = 120000 / 20
c = 12000/2
c = 6000
montante
M = c+j
M = 6000+1200
M = 7200
(6x-2)(6x-2) = 36x-12x-12x+4 = 36x+4
Adding together the shorter two sides results in 17 m. If these two sides were laid end to end, the sum of their sides (17 m) would be less than the length of the third side. Thus, NO triangle could be constructed with this set of line segments.