(i) (a²-b²)² = (a²)-2xa²xb²+(b²)+(b²)² [Using identity (a-b)²=a²-2ab+b²]
= a⁴-2a²b²+b⁴
(ii) (2x+5)²-(2x-5)² =(2x)²+2X2xX5+(5)²-[(2x)-2X2xX5+(5)²
[Using identities (a+b)² = a²+2ab+b² and (a-b)²=a²-2ab+b²
= 4x²+20x+25x-[4x²-20x+25]
= 4x²+20x+25x-4x²+20x-25
= 40x

Class 8 Maths Chapter 9 Exercise 9.5 Solution in Video

for more answers vist to:
https://www.tiwariacademy.com/ncert-solutions/class-8/maths/chapter-9/