y=2x−9x2
Comparing above equation with general equation of trajectory of projectile y=xtanθ(1−Rx)
tanθ=2
⇒sinθ=52 or cosθ=51
θ=sin−1(52) or θ=cos−1(51)
And R = 2/9
R=gv02sin2θ=92
After substituting the value for g and sin 2θ. We get v0=53 m/s