Answer
$y=-\frac{1}{98}(x-70)^{2}+50$
Work Step by Step
$y=a(x-h)^{2} + k$
Vertex (h,k) = (70,50)
->$y=a(x-70)^{2}+50$
So Landing point is (140,0)
-> $0=a(140-70)^{2}+50$
-> $0= 4900 a + 50 $
-> $a= - \frac{50}{4900} $
=$- \frac{1}{98}$
$y=-\frac{1}{98}(x-70)^{2}+50$
