Question

Expand using suitable Identity : 16a4 - 81

Answer 1

Step-by-step explanation:

i hope it may help you ....

Answer 2

Step-by-step explanation:

16$a^{4}$ - 81          [Expanding to its factorised standard form]

= [$(4a^{2} )^{2}$ - $(9)^{2}$  ]      →      [∵ $a^{2}$ - $b^{2}$ = (a+b)(a-b)]  

=  ($4a^{2}$ + 9) ($4a^{2}$ - 9)  

=  ($4a^{2}$ + 9) [$(2a)^{2}$ - ($3^{2}$) ]  →     [∵ $a^{2}$ - $b^{2}$ = (a+b)(a-b)]    

=  ($4a^{2}$ + 9) (2a+3) (2a-3) (Ans)