[填空题]
When a coin is thrown fromjkrfsep6+0j zd qae;, 85n9o u the top of a skysc n1xo 833:6ysn7p 6 hyhtya.m v9lnrudraper, its height above the ground after t seconds is given by s( 3uhmd.syva8 r6y7xy 3on6tn1 pn9:hlt)=at$^2$+bt+c , where a,b,c∈R and s(t) is measured in metres. After 1 second, the coin is 179.3 m above the ground; after 2 seconds, 188.2 m; after 6 seconds, 159.8 m.
1.1.Write down a system of three linear equations in terms of a, b and c.
1.2.Hence find the values of a, b and c.
Hence we find a=− ,b= ,c=
2.Find the height of the skyscraper.
s(t)= m.
3.Find the time it takes for the coin to hit the ground.
t is(≈) seconds.
