What are the factors of x2+4x+3

If I read this right, this problem is x^2 + 4x + 3

When the lead coefficient is 1 for a quadratic, you can simply start the problem by writing a pair of factors. Each factor will start with x. Now you want two numbers that multiply to the constant and add to the middle term.

(x + ?) (x + ?)

3 = 1*3, 1+3 = 4

So, x^2 + 4x + 3 = (x + 1) (x + 3)