how do i factor 36x^4-25x^2

Question

i need to know the how to work it out 

 

Answer 1

36x⁴ - 25x²

= x² ( 36x² - 25)

=x² (6x-5)(6x+5)......... using formula x² -y² =(x-y)(x+y)

Answer 2

36x⁴ - 25x² = x²[36x² - 25]

 

                = x²[(6x)² - (5)²] = x²(6x-5)(6x+5)