(a) You can parameterize C by the vector function
r(t) = (x(t), y(t) ) = P (1 - t ) + Q t = (2 - 2t, 7t )
where 0 ≤ t ≤ 1.
(b) From the above parameterization, we have
r'(t) = (-2, 7) ==> ||r'(t)|| = √((-2)² + 7²) = √53
Then
ds = √53 dt
and the line integral is
[tex]\displaystyle\int_C(9x(t)+5y(t))\,\mathrm ds = \boxed{\sqrt{53}\int_0^1(17t+18)\,\mathrm dt}[/tex]
(c) The remaining integral is pretty simple,
[tex]\displaystyle\sqrt{53}\int_0^1(17t+18)\,\mathrm dt = \sqrt{53}\left(\frac{17}2t^2+18t\right)\bigg|_{t=0}^{t=1} = \boxed{\frac{53^{3/2}}2}[/tex]
