Answer:
A
Step-by-step explanation:
A.
at 1.5 seconds
h=-16(1.5)²+30(1.5)+6
=-16×2.25+45+6
=-36+45+6
=15 ft
which is correct.
B.
h=-16(t²-30/16 t)+6
=-16(t²-30/16t+(15/16)²-(15/16)²)+6
=-16(t-15/16)²-16(-225/256)+6
=-16(t-15/16)²+225/16 +6
=-16(t-15/16)²+(225+96)/16
=-16(t-15/16)²+321/16
it is at maximum height when t=15/16 seconds
so B is not true.
C.
when t=15/16 seconds
h=321/16 ft=20 1/16 ft
height of fence=20 ft
so it will clear the fence.
C is not true.
D.
when h=0
-16t²+30t+6=0
8t²-15t-3=0
[tex]t=\frac{15\pm\sqrt{225-4 \times 8 \times (-3)} }{2 \times 8} \\=\frac{15 \pm \sqrt{225+96} }{16} \\=\frac{15\pm \sqrt{321} }{16} \\rejecting~negative~sign\\t=\frac{15+\sqrt{321}}{16} \approx. 2.057 seconds[/tex]
it hits the ground in 2.057 seconds
so D is not true.
