Question

fatoração 
 0, 81b4 - 36 

Answer 1

$0,81b^4-36=9(0,09b^4-4)$

Answer 2

$a^2-b^2=(a-b)(a+b)$

$0,81b^4-36=(0,9b^2)^2-6^2=(0,9b^2-6)(0,9b^2+6)$

$\rhd$ $0,9b^2-6=3(3b^2-2)$

$\rhd$ $0,9b^2+6=3(3b^2+2)$

$0,81b^4-36=3(0,3b^2-2)\cdot3(0,3b^2+2)$

$0,81b^4-36=\boxed{9(0,3b^2-2)(0,3b^2+2)}$