[填空题]
When a coin is thrown from9rb+k)mlz 1(0qivo aa the top of a skyscraper, i.7-rc9jkd1 jlzv2b(el rjiwb,-pnx.ts height above the ground after t seconds is given by bd (xz 2bci 7j.p.,1lv-e jj -kwrlrn9s(t)=$at^2$+bt+c, where a,b,c∈R and s(t) is measured in metres. After 11 second, the coin is 179.3 m above the ground; after 2 seconds, 188.2 m; after 66 seconds, 159.8 m.
1.(1)Write down a system of three linear equations in terms of a, b and c.
(2)Hence find the values of a, b and c. a = b = c =
2.Find the height of the skyscraper. s = m
3.Find the time it takes for the coin to hit the ground. t ≈