If f(x) = ax^2 + bx + c and f(0) = 1 and f(-1) = 3, what is a - b

If f(x) = ax^2 + bx + c and f(0) = 1 and f(-1) = 3, what is a - b

Evaluate f(0)
f(0) = a(0^2) + b(0) + c
f(0) = a(0) + b(0) + c
f(0) = c

Since f(0) = 1, we have
c = 1

Evaluate f(-1)
f(-1) = a(-1^2) + b(-1) + c
f(-1) = a(1) - b + c
f(-1) = a - b + c

Since f(-1) = 3, we have:
a - b + c = -3

We learned above that f(0) = 1, so c = 1. Plug c = 1 into f(-1)
a - b + 1 = -3

Subtract 1 from each side:
a - b + 1 - 1 = -3 - 1

Cancel the 1's on the left side and we get:
a - b = -4