Question

How do you factor `49t^2 - 81s^2`?

Answer 1

Can be: `(7t+9s)(7t-9s)`

Explanation:

Both the terms you have are squares so that you can use:
`a^2-b^2=(a+b)(a-b)`
in your case:
`49t^2-81s^2=(7t+9s)(7t-9s)`