Answer:
The correct option is 3.
Explanation:
In option 1,
The given equation is
![3x^2-4x-1=(3x+1)(x-1)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/myrkxip6ojdnrff5wnp60ky6309ddvpeqh.png)
Simplify the right sides.
![3x^2-4x-1=3x(x-1)+1(x-1)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/wmbic7b0ztb4xsndw7q96sahfdqhml5zp7.png)
![3x^2-4x-1=3x^2-3x+1x-1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/lpdbxmfzq94wzw14v9rntexx8d82ws2xsp.png)
![3x^2-4x-1 \\eq 3x^2-2x-1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ovjrxgw5kjsnh6dq4y01ak419jawf7qrgi.png)
Since left hand side is not equal to right hand side, therefore option 1 is incorrect.
In option 2,
The given equation is
![3x^2-2x-1=(3x-1)(x+1)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/w2tm1zsn5qa8qdobwj4z6s8nn3ut7f48c5.png)
Simplify the right sides.
![3x^2-4x-1\\eq 3x^2+2x-1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/fwtyw17zzof9bmnhwxg5hthpu0qsacuq4u.png)
Since left hand side is not equal to right hand side, therefore option 2 is incorrect.
In option 3,
The given equation is
![3x^2-4x+1=(3x-1)(x-1)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/a6v80xljrv453f08ic4agyfkyczi1v54wm.png)
Simplify the right sides.
![3x^2-4x+1=3x^2-4x+1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/dnutlc10bdc9uq7qx6dm7c03fp6rxahfyk.png)
Since left hand side is equal to right hand side, therefore option 3 is correct.
In option 4,
The given equation is
![3x^2-2x+1=(3x-1)(x-1)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/kl409um9by9hrkkb6a5rye495su99is48u.png)
Simplify the right sides.
![3x^2-2x+1\\eq 3x^2-4x+1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/n2hiuzgv3iw2dju6ul07pqhlasssw3lzcy.png)
Since left hand side it not equal to right hand side, therefore option 4 is incorrect.