Hint: it's not 16x^2-25
Take a look at Kuai's solution to the previous problem, and note the signs.
(4x-5)^2
3 answers
(4x-5)(4x-5)
16x^2 -20x -20x + 25
= 16x^2 -40x +25
16x^2 -20x -20x + 25
= 16x^2 -40x +25
Will it be 16x^2-40x+25