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stiks02 [169]
3 years ago
11

The period of a pendulum is the time the pendulum takes to swing back and forth one full time. The function I = 0.81t^2 relates

the length l in feet of a pendulum to the time t in seconds that it takes to swing back and forth. The convention center in Portland, Oregon, has the longest pendulum in the U.S. The pendulum’s length is 90 ft. Find the period for this pendulum.
a. 8.5 seconds
b. 10.5 seconds
c. 90 seconds
d. 111 seconds
Mathematics
1 answer:
kogti [31]3 years ago
5 0

Answer:

b.  t = 10.5 seconds.

Step-by-step explanation:

l = 0.81t^2

90 = 0.81t^2

t^2 = 90 / 0.81

t^2 = 111

t = 10.5 seconds.

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Consider the equation below. (If an answer does not exist, enter DNE.) f(x) = x3 − 6x2 − 15x + 2 (a) Find the interval on which
Burka [1]

Answer:

a) (-\infty, -1) \cup (5, \infty)

b) (-1,5)

Step-by-step explanation:

The first step to solve this question is finding the roots of the derivative of x.

Solving a quadratic equation:

Given a second order polynomial expressed by the following equation:

ax^{2} + bx + c, a\neq0.

This polynomial has roots x_{1}, x_{2} such that ax^{2} + bx + c = a(x - x_{1})*(x - x_{2}), given by the following formulas:

x_{1} = \frac{-b + \sqrt{\bigtriangleup}}{2*a}

x_{2} = \frac{-b - \sqrt{\bigtriangleup}}{2*a}

\bigtriangleup = b^{2} - 4ac

In this question:

f(x) = x^{3} - 6x^{2} - 15x + 2

So

f'(x) = 3x^{2} - 12x - 15

Finding the roots:

3x^{2} - 12x - 15 = 0

Simplifying by -3

x^{2} - 4x - 5 = 0

So a = 1, b = -4, c = -5

Then

\bigtriangleup = (-4)^{2} - 4*1*(-5) = 36

x_{1} = \frac{-(-4) + \sqrt{36}}{2} = 5

x_{2} = \frac{-(-4) - \sqrt{36}}{2} = -1

So the function can be divided in three intervals.

They are:

Less than -1

Between -1 and 5

Higher than 5

In which it increases and which it decreases?

Less than -1

Lets find the derivative in a point in this interval, for example, -2

f'(x) = 3x^{2} - 12x - 15

f'(-2) = 3*(-2)^{2} - 12*(-2) - 15 = 21

Positive.

So in the interval of (-\infty, -1), the function increases.

Between -1 and 5

Will choose 0.

f'(x) = 3x^{2} - 12x - 15

f'(0) = 3*(0)^{2} - 12*(0) - 15 = -15

Negative.

So in the interval of (-1,5), the function decreases.

Higher than 5

Will choose 6.

f'(x) = 3x^{2} - 12x - 15

f'(6) = 3*(6)^{2} - 12*(6) - 15 = 21

Positive

So in the interval of (5, \infty), the function increases.

(a) Find the interval on which f is increasing.

Using interval notation

(-\infty, -1) \cup (5, \infty)

b) Find the interval on which f is decreasing.

(-1,5)

5 0
3 years ago
HELP ME WITH THIS MATH ...................................
Alex17521 [72]

Answer:

The answer is B: -5

Explanation:

Look at the Y line and see where the line intersects with the Y line at -5

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