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atroni [7]
3 years ago
13

A rock is thrown from the top of a tall building.The distance in feet between the rock and the ground t seconds after thrown is

given by d = -16t2 -4t + 412. How long after the rock is thrown is it 407 feet from the ground?
Mathematics
1 answer:
marusya05 [52]3 years ago
4 0

Answer:

0.448 seconds

Step-by-step explanation:

d = -16t² -4t + 412

find t when d = 407

substituting d = 407 into the equation:

407 = -16t² -4t + 412 (subtract 407 from both sides)

-16t² -4t + 412 - 407 = 0

-16t² -4t + 5 = 0 (multiply both sides by -1)

16t² + 4t - 5 = 0  

solving using your method of choice (i.e completing the square or using the quadratic equation), you will end up with

t = (-1/8) (1 + √21)= -0.70 seconds (not possible because time cannot be negative)

or

t = (-1/8) (1 -√21) = 0.448 seconds (answer)

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$800 is deposited in an account
Sergeeva-Olga [200]

Answer:

The balance after four years is $1129.27

Step-by-step explanation:

The formula for compound interest, including principal sum, is A=P(1+\frac{r}{n})^{nt}

  • A = the future value of the investment/loan, including interest
  • P = the principal investment amount (the initial deposit or loan amount)
  • r = the annual interest rate (decimal)
  • n = the number of times that interest is compounded per unit t
  • t = the time the money is invested or borrowed for

∵ $800 is deposited in an account

∴ P = 800

∵ The account pays 9% annual interest

∴ r = 9% = 9 ÷ 100 = 0.09

∵ The interest is compounded annually

∴ n = 1

∵ The time is 4 years

∴ t = 4

- Substitute the values of P, r, n, and t in the formula above

∵ A=800(1+\frac{0.09}{1})^{(1)(4)}

∴ A=800(1.09)^{4}

∴ A = 1129.265

∴ The balance after four years is $1129.27

8 0
3 years ago
In triangle ABC , m angle A=(3x)^ , m angle B=(3x+10)^ , and m angle C=(4x-30)^ Find m m angle C
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Answer:

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Step-by-step explanation:

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10x°/10=200°/10

x°=20°

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Step-by-step explanation:

None. √-21 is not a real number.

7 0
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Size got it right because it’s multiplied by 100
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