Vf^2=Vi^2+(-g)(Yf-Yi)

Question

Maximum Height derive from kinematic formula

Answer 1

I am not sure what your question is but the function is incorrect. There is a 2 missing.

v_y² = v_oy² + 2a_yΔy where a_y= -g and Δy = y_f - y_o

_{You were missing the 2.}

At max height v_y is zero ( vertical velocity at apex).