Explain why the polynomial 144x2 − 200x + 81 is not a perfect square.

The square root of 144x^2 = 12 x
and square root of + 81 = 9 or -9

if  this polynomial were a perfect square then its factors would be 
(12x - 9)(12x - 9)

but its not a perfect squre because (12x - 9)(12x - 9)  = 144x^2 - 216x + 81.