Question

How do you factor by grouping `12a^3+20a^2-48a`?

Answer 1

Factoring by grouping is not a method that is reasonable for an expression with 3 terms (perhaps a 4th term was intended(?))

This expression, `12a^3+20a^2-48a`, can be factored fairly simply

Extract the obvious common factor
`(4a)(3a^2+5a-12)`
and from there
`(4a)(3a-4)(a+3)`