Which equation is equivalent

(4x^2 +9) (4x^2 -9) =0

Step-by-step explanation:

16x^4 - 81 =0

Rewriting

(4x^2) ^2 - 9^2 =0

This is the difference of squares a^2 -b^2 = (a+b)(a-b)

(4x^2 +9) (4x^2 -9)=0

b) the dogs need to shift their focus to human scent.