The given function is .

                         (Substitute f(x) = 0)

Apply multiplication property of addition: If a = b then .

And multiply each side by .

Apply zero product property: .

The factors of 12: 4, 3 (or) 3, 4 (or) 12, 1 (or) 1, 12.

The correct factors are 4, 3 and 12, So m = 4, n = 3.

Then write the factors form .

             (Group terms with common factors)

                 (Factors the grouping terms)

                         (Take out common term )

Apply zero product property: If then a = 0 (or) b = 0.

Solve for first factor .

Apply subtraction property of equality: If a = b then .

                             (Subtract 3 from each side)

Solve for second factor .

Apply subtraction property of equality: If a = b then .

                            (Add 4 to each side)

The roots are 3, and 4.