Projectile motion, initial angle and velocity Question: A projectile motion passes $(16i+7.1j)$, $(0i+0j)$ and $(32i+4.4j)$. Determine the initial speed and velocity. (At the origin) 
My attempt: I converted the $i$ and $j$ in $x$ and $y$ to find the parabolic cartesian formula for the projectile. However, while this helped determine the angle of projection, it didn’t show me the initial velocity, so I’m stuck. 

If $v_0$ is the initial velocity, $g$ the acceleration, and $\alpha$ the initial angle ($\alpha=( \vec{i},  \vec{v_0}))$ then $ y=\frac{-g}{2v_0^2cos^2\alpha}X^2+X\tan\alpha$. You can deduce $\tan\alpha=\frac{3}{4}$ and  $\frac{-g}{2v_0^2cos^2\alpha}=-\frac{49}{2560}$ $\Rightarrow, v_0 =\sqrt{\frac{2560g}{98\cos^2\alpha}}=20m.s^{-1}$
