To find the intersection points, you take x^2 - 4x + 9 = -2x + 17
This gives x^2 - 2x - 8 = 0,
which factorises to (x - 4)(x + 2) = 0, giving the solutions x = 4 or x = -2
From the graph, we can see that x is positive, meaning x = 4, so a = 4.
Substituting x = 4 into y = -2x + 17, we get y = -2(4) + 17 = 9, so b = 9.
a + b = 4 + 9 = 13. The answer is B.