(3x + 1)(x - 5)
x = ? 42 = x squared minus x
(x2 + 1)(x2 - 2)
3x squared minus 25x minus 28
For a start, you can look for a common factor, and separate it. What remains (the other factor) will only be a polynomial of degree 2; I assume you already learned how to factor that.
4x2 - 4 is a polynomial of degree two.
A polynomial.
There are no rational factors.
2(4x - 3)
2(4m-3)
(a + 3)(a - 3)
5a2-15 = 5 (a2-3) = 5 (a-sqrt(3))(a+sqrt(3)) as a2-b2=(a-b)(a+b)