You have an equal sign in the middle of one of your polynomials, I'm going to guess it is supposed to be a + since = & + are on the same key.
Note: You can't solve this because it is not an equation, meaning it doesn't equal anything, however you can simplify it.
(2a² + 4a + 1) + (a² - 6a - 4)
2a² + 4a + 1 + a² - 6a - 4
2a² + a² + 4a - 6a + 1 - 4
3a² - 2a - 3
Now it is simplified. Can you see what I mean by you can't solve it? If doesn't = anything. I can say a = 1, then I get 3 - 2 - 2 = -2, so is that the answer? I don't know because I can also say a = 2 & get 12 - 4 - 3 = 5. Or a = 0 & get 0 - 0 - 3 = -3. All of them work (as will any number I put in there), so which is the answer? Any of them can be the answer, so this can not be solved.
For this to be solved, it would need to look more like
3a² - 2a - 3 = 7, then you could solve it by factoring or using the quadratic equation.