I will guess that "d1" is the common difference. If so, then d1 = -2, because the values are getting smaller.

When n = 1, then an = -2(1)^2 - 3 = -2 - 3 = -5. To find the next few terms, plug in 2 for n, then 3 for n, etc, etc.

Do you know how tosolve linear equations? (Yes, this is quadratic, but the first step would be one that you would have learned for linear equations, and the answer would be fairly obvious after that one step....)

Do you know how to solve systems of linear equations? Because you can plug n = 1, n = 2, and n = 3 into the generic quadratic equation, plug in the output values, and thus create a system of linear equations where you'd solve for the coefficients of an^2 + bn + c:

a + b + c = 3

4a + 2b + c = 4

9a + 3b + c = -1