Their sum = 8 and their product is 4^2 + 1 = 17.
So, the equation is x^2 - 8x + 17 = 0 (ie x^2 - (r1+r2)x + r1 r2 =0
Forget any any other way of solutions more than two lines about this kind of
baby level questions.
Also, there is no any reason you did not know the typing '+' sign.