We're told the line intersects twice, which means the quadratic above has two distinct real solutions. Its discriminant must then be positive, so we know
We can tell from the quadratic equation that has its vertex at the point (3, 6). Also, note that
and
so the furthest to the right that extends is the point (5, 2). The line passes through this point for . For any value of , the line passes through either only once, or not at all.
For matrix subtraction, you subtract the corresponding cell of the second matrix from the first. So, looking at the first spot, you have 4 (from the first matrix) - 4 (from the second matrix) = 0 (the first number in the output matrix). Continuing that for the next spot, -4 - -3 = -4 + 3 = -1. Finally, -2 - 5 = -7. This means your answer is [0 -1 -7].