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Regarding this problem, notice that both these formulas describe the projection of the position to the vertical direction.
They do not describe a trajectory of the ball, which is usually a parabola in (x,y)-plane.
In football, it is a rare case, when the ball moves vertically up --- so the question and the problem itself are not very realistic.
If, nevertheless, these circumstances do not embarrass you, then consider this equation
-4.9*π‘^2 + 18π‘ + 0.8 = -1.43t + 4.26
and solve it for t.
Solving this equation is a mechanical work, so I leave it to you.
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In my personal view, the posed problem is not adequate to reality.