Suppose a rock is thrown off of a bridge into the river 120 feet below. the height, h, in feet of the rock above the river is given by h = ? 16t2 + 84t + 120, where t is the time in seconds. how long does it take the rock to splash into the river below?

  about 6.418 seconds

Step-by-step explanation:

You apparently want to find t when h=0:

  0 = -16t^2 +84t +120

  0 = 4t^2 -21t -30 . . . . . . divide by -4

  t = (-(-21 ±√((-21)² -4(4)(-30)))/(2(4)) = (21±√921)/8 . . . . only the positive time is of interest

  t = 2.625+√14.390625 ≈ 6.419 . . . . seconds

It takes about 6.42 seconds for the rock to hit the water.

step-by-step explanation:

a.   since the profit made in 2012 is equal to the profit made in 2014, the profit is           symmetric about the line y = 120,000.

step-by-step explanation:

given that megan owns a clothing boutique.

the profits of 2010, 11, are recorded and shown as follows:

years since     2010 0     1     2     3       4       5

profits made in 1000's   39       84     111     120   111     84

we find that profit gradually increases form 2010 to 2013 upto 120,   then starts decreasing.

the profits for 2012 and 2014 are the same while that of 2011 and 2015 are also the same.

this shows that there is symmetry about the line profit = 120000

hence answer is:

a.   since the profit made in 2012 is equal to the profit made in 2014, the profit is           symmetric about the line y = 120,000.

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