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3 years ago

How to solve which number completes the square of the expression belo? 2x^2-3x+ 1. 9/8 2. 9 3. -9/2 4. 9/16

Mathematics

1 answer:

choli [55]3 years ago

7 0

Answer: 1. $\dfrac{9}{8}$ .

Step-by-step explanation:

The given expression $2x^2-3x+1$

Using completing the square method.

First, we divide the entire expression by 2 and write in the form of $x^2+bx=c$ , we get

$x^2-\dfrac{3}{2}x+\dfrac{1}{2}$

Such that $b=\dfrac{3}{2}\ \ \ , c=\dfrac{1}{2}$

Now add and subtract $(\dfrac{b}{2})^2$ on both sides.

$(\dfrac{b}{2})^2=(\dfrac{\dfrac{3}{2}}{2})^2\\\\=(\dfrac{3}{2\times2})^2\\\\=(\dfrac{3^2}{4^2})\\\\=\dfrac{9}{8}$

Here, we add and subtract $\dfrac{9}{8}$ .

Hence, the correct answer is 1. $\dfrac{9}{8}$ .

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3 years ago

The Wall Street Journal reports that 33% of taxpayers with adjusted gross incomes between $30,000 and $60,000 itemized deduction

Len [333]

Answer:

(a) n : 20 50 100 500

P (-200 < X - μ < 200) : 0.2886 0.4444 0.5954 0.9376

(b) The correct option is (b).

Step-by-step explanation:

Let the random variable X represent the amount of deductions for taxpayers with adjusted gross incomes between $30,000 and $60,000 itemized deductions on their federal income tax return.

The mean amount of deductions is, μ = $16,642 and standard deviation is, σ = $2,400.

Assuming that the random variable X follows a normal distribution.

(a)

Compute the probability that a sample of taxpayers from this income group who have itemized deductions will show a sample mean within $200 of the population mean as follows:

For a sample size of n = 20

$P(\mu-200$

$=P(-0.37$

For a sample size of n = 50

$P(\mu-200$

$=P(-0.59$

For a sample size of n = 100

$P(\mu-200$

$=P(-0.83$

For a sample size of n = 500

$P(\mu-200$

$=P(-1.86$

n : 20 50 100 500

P (-200 < X - μ < 200) : 0.2886 0.4444 0.5954 0.9376

(b)

The law of large numbers, in probability concept, states that as we increase the sample size, the mean of the sample ( $\bar x$ ) approaches the whole population mean ( $\mu_{x}$ ).