Question 640486
Take the square root of 16 to get 4. Take the square root of 25 to get 5.


Now multiply 4 and 5 to get 20. Double this to get 40.


So 40x is the missing term, which means that


16x^2 + _<u><font color="red">40x</font></u>_+ 25


is a perfect square trinomial.