3/4(8g-1/4-2/3g)=<br> Simplify the expression

A poll of 1,000 randomly selected registered voters was taken and 680 responded that they favor candidate X for mayor (p 1 = 0.6

Zielflug [23.3K]

Answer:

The interval (-0.0199, 0.0510) represents the region of values where the true difference (in population terms now) between the initial proportion of registered voters that favour candidate X and the proportion of registered voters that favour candidate X just before election can take on with a confidence level of 90%.

Step-by-step explanation:

Confidence Interval for the population proportion is basically an interval of range of values where the true population proportion can be found with a certain level of confidence. It is usually obtained from the sample.

p₁ represents the proportion of registered voters that favour candidate X in the initial poll, way before the election.

p₂ represents the proportion of registered voters that favour candidate X in the poll just before the election.

So, for this question the confidence interval for the true difference between the population proportion of registered voters that favour candidate X way before the elections and the population proportion that favour candidate X just before the election lies within (-0.0199, 0.0510) with a confidence interval of 90%.

Confidence interval is calculated mathematically as thus:

Confidence Interval = (Difference in Sample proportion) ± (Margin of error)

Margin of Error is the width of the confidence interval about the difference in the two sample proportions.

It is given mathematically as,

Margin of Error = (Critical value) × (standard Error)

Critical value = 1.645 (obtained from the z-tables because the sample size is large enough to ignore that information about the population standard deviation isn't given and t-critical value approximates z-critical value)

Hope this Helps!!!

4 0

3 years ago

2. Consider the circle x^2−4x+y^2+10y+13=0. There are two lines tangent to this circle having a slope of 2/3.

likoan [24]

Answer:

a) The coordinates are (0.431, -2.646) and (3.568,-7.354)

b) The tangent lines are

l₁ = (x-0.431)*2/3 - 2.646

l₂ = (x-3.568)2/3 - 7.354

Step-by-step explanation:

First, lets complete squares, by taking for each cordinate the square of a linear expression

0= x²−4x+y²+10y+13 = (x-2)²+ 4 + (y+5)²-25+13 = (x-2)²+(y+5)² - 8

Hence (x-2)² + (y+5)² = 8

Lets put y in function of x. We should obtain 2 functions f and g that represent the circle.

(y+5)² = 8 - (x-2)² = -x² + 4x + 4

$y = ^+_- \sqrt{-x^2+4x+4} -5$

Thus

$f(x) = \sqrt{-x^2+4x+4} - 5$

$g(x) = -\sqrt{-x^2+4x+4} - 5$

Lets find the derivate of each function and the points in which they reach the value 2/3. In those points the tangent line will have a slope of 2/3.

We may just find the values of x which the derivate of f is either 2/3 or -2/3.

$\frac{-x+2}{\sqrt{-x^2+4x+4}} = ^+_-\frac{2}{3} \Leftrightarrow \frac{x^2-4x+4}{-x^2+4x+4} = \frac{4}{9} \Leftrightarrow 9(x^2-4x+4) = 4(-x^2+4x+4) \\\Leftrightarrow 13x^2-52x+20 = 0$

The quadratic has roots

$\frac{52 ^+_-\sqrt{1664}}{26}$

one root is 3.568, which corresponds with g, and the other root is 0.431, corresponding to f.

Also g(3.568) = - 7.354 and f(0.431) = -2.646

This means that the coordinates are (0.431 , -2.646), (3.568 , -7.354) and the tangent lines are

l₁ = (x-0.431)*2/3 - 2.646

l₂ = (x-3.568)2/3 - 7.354

5 0

3 years ago

3x-y+z=-15<br> x+2y-z=1<br> 2x+3y-2z=0

Kazeer [188]

I assume you are being asked to solve these equations. Since there wasn't an explanation as to how you are expected to solve them, I chose to demonstrate how to use a calculator matrix function. You can find matrix calculators online. My instructions are for a TI-84
Push the blue 2nd button then push x^-1 button (it says matrix above this button in blue)
Arrow over to edit to change the dimensions of the matrix and to put in your values. You have 3 equations (3 rows) and 4 terms (4 columns) so you put a 3x4 in for the dimension and the coefficients (see images).
You use the rref option in the math column in matrix to calculate the answer.
The numbers at the end are the solutions. x = -4, y = 2, z = -1