Answer:
(5x²+4y)(5x²-4y)
Explanation:
25x4 -16y2 looks like the the difference of two sqaures where everything to be factorized has a square root.
Let's try and reduce it , so we'll understand.
25x4 -16y2 = 5x²5x² - 4y4y
Factorizing the more gives us
= (5x²+4y)(5x²-4y)