Question

How do you factor `16m^4 - 81`?

Answer 1

`16m^4-81`

Factorize:
`=(4m^2)^2-(9)^2`

Recall: `(a)^2-(b)^2=(a+b)(a-b)`

`=(4m^2+9)(4m^2-9)`
`=(4m^2+9)[(2m)^2-(3)^2]`

ANSWER:
`color(green)[=(4m^2+9)(2m+3)(2m-3)`