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3 years ago

What is the focus of the parabola given by `-(1)/(4)(y + 2)^2 = (x −1)`? A. (-1, 2) B. (1, -2) C. (0, -2) D. (0, 2)

Mathematics

2 answers:

katrin [286]3 years ago

5 0

The correct answer is that the focus is, <u><em>(0,−2)</em></u>

Amanda [17]3 years ago

5 0

Answer:

The correct option is C.

Step-by-step explanation:

The given equation is

$-\frac{1}{4}(y+2)^2=(x-1)$

Multiply both the sides by -4.

$(y+2)^2=-4(x-1)$ .... (1)

Where, (h,k) is vertex and (h+p,k) is focus.

The standard form of a parabola is

$(y-k)^2=4p(x-h)$ ..... (2)

From (1) and (2), we get

$k=-2,h=1,4p=-4\Rightarrow p=-1$

The focus of the parabola is

$(h+p,k)=(1-1,-2)=(0,-2)$

The focus of the given parabola is (0,-2). Therefore the correct option is C.

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2 years ago

Plane R contains which of the following?

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The letter R is on the yellow section, which indicates the yellow area is plane R.

Now see what points and lines are on the yellow sections.

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3 years ago

Samuel is solving the equation 3(x - 1) + 4 = 2 - (x + 3). Which equivalent equations might Samuel use? Select the TWO correct a

mote1985 [20]

A= 3, and 4. (c & d)

1. Solve the Equation: $3(x - 1) + 4 = 2 - (x + 3)\\$ , to get

------------------------------------------

1a. Use the distributive property to multiply 3 by x−1.

$3x−3+4=2−(x+3)$

1b. Add −3 and 4 to get 1.

$3x+1=2−(x+3)$

1c. To find the opposite of x+3, find the opposite of each term.

$3x+1=2−x−3$

1d. Subtract 3 from 2 to get −1.

$3x+1=−1−x$

1e. Add x to both sides.

$3x+1+x=−1$

1f. Combine 3x and x to get 4x.

$4x+1=−1$

1g. Subtract 1 from both sides.

$4x=−1−1$

1h. Subtract 1 from −1 to get −2.

$4x=−2$

1i. Divide both sides by 4.

$x=4−2$

1j. Reduce the fraction 4−2=−0.5 to lowest terms by extracting and canceling out 2.

$x=−21$ or x = -21

-------------------------------------

Now that you know the answers, solve the others:

2. A= 1, so this is wrong. How I solved it is shown below:

-----------------------------------

1a. Add −3 and 4 to get 1.

3x+1=2−x+3

1b. Add 2 and 3 to get 5.

3x+1=5−x

1c. Add x to both sides.

3x+1+x=5

1d. Combine 3x and x to get 4x.

4x+1=5

1e. Subtract 1 from both sides.

4x=5−1

1f. Subtract 1 from 5 to get 4.

4x=4

1g.Divide both sides by 4.

x=44

1h. Divide 4 by 4 to get 1.

x=1

----------------------------

3. A= .5, so it is Correct. Work below

-----------------------------

3a. Add x to both sides.

$3x+3+x=5$

3b. Combine 3x and x to get 4x.

$4x+3=5$

3c. Subtract 3 from both sides.

$4x=5−3$

3d. Subtract 3 from 5 to get 2.

$4x=2$

3e. Divide both sides by 4.

$x=42$

3f. Reduce the fraction 42=0.5 to lowest terms by extracting and canceling out 2.

$x=21$ (A = 1/2 or .5)

-----------------------------

4. A= .5, so it is correct. Work below. Now we have our 2, so we don't need to do it again.

-------------------------------

4a. Add −1 and 4 to get 3.

$3x+3=2−x+3$

4b. Add 2 and 3 to get 5.

$3x+3=5−x$

4c. Add x to both sides.

$3x+3+x=5$

4d. Combine 3x and x to get 4x.

$4x+3=5$

4e. Subtract 3 from both sides.

$4x=5−3$

4f. Subtract 3 from 5 to get 2.

$4x=2$

4g. Divide both sides by 4.

$x=\frac{2}{4}$

4h. Reduce the fraction 42=0.5 to lowest terms by extracting and canceling out 2.

$x=\frac{1}{2}$

7 0

3 years ago

A standard weight known to weigh 10 grams. Some suspect bias in weights due to manufacturing process. To assess the accuracy of

notsponge [240]

Answer:

a) The 98% confidence interval for the mean weight is between 10.00409 grams and 10.00471 grams

b) 49 measurements are needed.

Step-by-step explanation:

Question a:

We have that to find our $\alpha$ level, that is the subtraction of 1 by the confidence interval divided by 2. So:

$\alpha = \frac{1 - 0.98}{2} = 0.01$

Now, we have to find z in the Ztable as such z has a pvalue of $1 - \alpha$ .

That is z with a pvalue of $1 - 0.01 = 0.99$ , so Z = 2.327.

Now, find the margin of error M as such

$M = z\frac{\sigma}{\sqrt{n}}$

In which $\sigma$ is the standard deviation of the population and n is the size of the sample.

$M = 2.327\frac{0.0003}{\sqrt{5}} = 0.00031$

The lower end of the interval is the sample mean subtracted by M. So it is 10.0044 - 0.00031 = 10.00409 grams

The upper end of the interval is the sample mean added to M. So it is 10 + 0.00031 = 10.00471 grams

The 98% confidence interval for the mean weight is between 10.00409 grams and 10.00471 grams.

(b) How many measurements must be averaged to get a margin of error of +/- 0.0001 with 98% confidence?

We have to find n for which M = 0.0001. So

$M = z\frac{\sigma}{\sqrt{n}}$

$0.0001 = 2.327\frac{0.0003}{\sqrt{n}}$

$0.0001\sqrt{n} = 2.327*0.0003$

$\sqrt{n} = \frac{2.327*0.0003}{0.0001}$

$(\sqrt{n})^2 = (\frac{2.327*0.0003}{0.0001})^2$

$n = 48.73$

Rounding up

49 measurements are needed.

7 0

3 years ago