Solution 2. (4): let y = (1+x) 12, then x->; Y- > is 0; 1, the original formula = (y 3-1)/(y 4-1) = [(y-1) (y 2+y+1)]/(y-)

Solution 3. If the original formula is multiplied by (1-x), then the original formula = ((1-x 2) (1+x 2) ... (1+x2n))/(1-2).

Considering that you are a freshman, you may not have studied Robida's law, Taylor's expansion and other methods, so I will provide you with this method. I hope I can help you and adopt the best answer.