how do i solve 4(a-1)^2 ?
You can not solve it because there is no equal sign.
But, you can expand and simplify it.
$$4(a-1)^2\\=4*(a-1)(a-1)\\=4*[a(a-1)-1(a-1)]\\=4*[a^2-a-a+1]\\=4*[a^2-2a+1]\\$$
Can you take it from there?