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Leya [2.2K]
1 year ago
6

An x-method chart shows the product a c at the top of x and b at the bottom of x. Below the chart is the expression a x squared

+ b x + c. Consider the trinomial 9x2 + 21x + 10. What value is placed on top of the X? What value is placed on the bottom of the X? What is the factored form of 9x2 + 21x + 10?
Mathematics
2 answers:
natima [27]1 year ago
7 0

Answer:

the correct answers are

What value is placed on top of the X?  90

What value is placed on the bottom of the X? 21

What is the factored form of 9x2 + 21x + 10?  (3x + 2)(3x + 5)

Step-by-step explanation:

i got it right, hope this helps :D

Viktor [21]1 year ago
4 0

Answer:

What value is placed on top of the X?

✔ 90

What value is placed on the bottom of the X?

✔ 21

What is the factored form of 9x2 + 21x + 10?

✔ (3x + 2)(3x + 5)

Step-by-step explanation:

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Example 4.5 introduced the concept of time headway in traffic flow and proposed a particular distribution for X 5 the headway be
exis [7]

Answer:

a. k = 3

b. Cumulative distribution function X, F(x)=\left \{ {0} , x\leq 1  \atop {1-x^{-3}, x>1}} \right.

c.  Probability when headway exceeds 2 seconds = 0.125

Probability when headway is between 2 and 3 seconds = 0.088

d. Mean value of headway = 1.5

Standard deviation of headway = 0.866

e.  Probability that headway is within 1 standard deviation of the mean value = 0.9245

Step-by-step explanation:

From the information provided,

Let X be the time headway between two randomly selected consecutive cars (sec).

The known distribution of time headway is,

f(x) = \left \{ {\frac{k}{x^4} , x > 1} \atop {0} , x \leq 1 } \right.

a. Value of k.

Since the distribution of X is a valid density function, the total area for density function is unity. That is,

\int\limits^{\infty}_{-\infty} f(x)dx=1

So, the equation becomes,

\int\limits^{1}_{-\infty} f(x)dx + \int\limits^{\infty}_{1} f(x)dx=1\\0 + \int\limits^{\infty}_{1} {\frac{k}{x^4}}.dx=1\\0 + k \int\limits^{\infty}_{1} {\frac{1}{x^4}}.dx=1\\k[\frac{x^{-3}}{-3}]^{\infty}_1=1\\k[0-(\frac{1}{-3})]=1\\\frac{k}{3}=1\\k=3

b. For this problem, the cumulative distribution function is defined as :

F(x) = \int\limits^1_{\infty} f(x)dx +  \int\limits^x_1 f(x)dx

Now,

F(x) = 0 +  \int\limits^x_1 {\frac{k}{x^4}}.dx\\= 0 +  \int\limits^x_1 3x^{-4}.dx\\= 3 \int\limits^x_1 x^{-4}dx\\= 3[\frac{x^{-4+1}}{-4+1}]^3_1\\= 3[\frac{x^{-3}}{-3}]^3_1\\=(\frac{-1}{x^3})|^x_1\\=(-\frac{1}{x^3}-(\frac{-1}{1}))=1- \frac{1}{x^3}=1-x^{-3}

Therefore the cumulative distribution function X is,

F(x)=\left \{ {0} , x\leq 1  \atop {1-x^{-3}, x>1}} \right.

c. Probability when the headway exceeds 2 secs.

Using cdf in part b, the required probability is,

P(X>2)=1-P(X\leq 2)\\=1-F(2)\\=1-[1-2^{-3}]\\=1-(1- \frac{1}{8})\\=\frac{1}{8} = 0.125

Probability when headway is between 2 seconds and 3 seconds

Using the cdf in part b, the required probability is,

P(2

≅ 0.088

d. Mean value of headway,

E(X)=\int\limits x * f(x)dx\\=\int\limits^{\infty}_1 x(3x^{-4})dx\\=3 \int\limits^{\infty}_1 x(x^{-4})dx\\=3 \int\limits^{\infty}_1 x^{-3}dx\\=3[\frac{x^{-3+1}}{-3+1}]^{\infty}_1\\=3[\frac{x^{-2}}{-2}]^{\infty}_1\\=3[\frac{1}{-2x^2}]^{\infty}_1\\=3[- \frac{1}{2x^2}]^{\infty}_1\\=3[- \frac{1}{2(\infty)^2}- (- \frac{1}{2(1)^2})]\\=3(\frac{1}{2})=1.5

And,

E(X^2)= \int\limits^{\infty}_1 x^2(3x^{-4})dx\\=3 \int\limits^{\infty}_1 x^{-2} dx\\=3[- \frac{1}{x}]^{\infty}_1\\=3(- \frac{1}{\infty}+1)=3

The standard deviation of headway is,

= \sqrt{V(X)}\\ =\sqrt{E(X^2)-[E(X)]^2} \\=\sqrt{3-(1.5)^2} \\=0.8660254

≅ 0.866

e. Probability that headway is within 1 standard deviation of the mean value

P(\alpha - \beta  < X < \alpha + \beta) = P(1.5-0.866 < X < 1.5 +0.866)\\=P(0.634 < X < 2.366)\\=P(X

From part b, F(x) = 0, if x ≤ 1

=1-(2.366)^{-3}\\=0.9245

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Dilly is 7 years younger than Dally. In 4 years time she will be half Dally’s age. What is the sum of their ages now?
Step2247 [10]

Answer:

<u>The sum of their ages now is 13</u>

Step-by-step explanation:

Dally's age = x

Dilly's age = x - 7

In 4 years time Dilly will be half Dally’s age, therefore:

Dilly's age plus four equals to half of Dally’s age plus four,

replacing with the values and variables we know:

x - 7 + 4 = (x + 4) /2

x - 3 = (x + 4) /2

2x - 6 = x + 4 (Multiplying by 2 at both sides)

2x - x = 4 + 6 (Like terms)

x = 10 ⇒ x - 7 = 3

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