\text{a)}
y' = 2x + b
\text{Since it's tangent to the x axis at 5,0 it means the gradient of the parabola at 5,0 is 0 because the gradient of the x axis is 0}
\therefore 0 = 2(5) + b \Rightarrow b = -10
\text{Figure out c easily by just subbing the point (5,0) in the original equation of the...