Subtract X2 + 8x +9

The amount of Jen’s monthly phone bill is normally

vredina [299]

Answer:

$P(19$

And we can find this probability with this difference and using the normal standard distribution

$P(-3$

Step-by-step explanation:

Let X the random variable that represent the amount of Jen monthly phone of a population, and for this case we know the distribution for X is given by:

$X \sim N(55,12)$

Where $\mu=55$ and $\sigma=12$

We are interested on this probability

$P(19$

And we can use the z score formula given by:

$z=\frac{x-\mu}{\sigma}$

Replacing the info we got:

$P(19$

And we can find this probability with this difference and using the normal standard distribution

$P(-3$

7 0

3 years ago

Which is the equation of a parabola with a directrix at y = −3 and a focus at (5, 3)?

kramer

Answer:

y = 1/12 (x − 5)²

Step-by-step explanation:

We can solve this graphically without doing calculations.

The y component of the focus is y = 3. Since this is above the directrix, we know this is an upward facing parabola, so it must have a positive coefficient. That narrows the possible answers to A and C.

The x component of the focus is x = 5. Since this is above the vertex, we know the x component of the vertex is also x = 5.

So the answer is A. y = 1/12 (x−5)².

But let's say this wasn't a multiple choice question and we needed to do calculations. The equation of a parabola is:

y = 1/(4p) (x − h)² + k

where (h, k) is the vertex and p is the distance from the vertex to the focus.

The vertex is halfway between the focus and the directrix. So p is half the difference of the y components:

p = (3 − (-3)) / 2

p = 3

k, the y component of the vertex, is the average:

k = (3 + (-3)) / 2

k = 0

And h, the x component of the vertex, is the same as the focus:

h = 5

So:

y = 1/(4×3) (x − 5)² + 0

y = 1/12 (x − 5)²

3 0

2 years ago

At a sand and gravel plant, sand is falling off a conveyor and onto a conical pile at a rate of 6 cubic feet per minute. The dia

Alla [95]

Answer:

$0.2122\text{ ft per min}$

Step-by-step explanation:

Let r be the radius ( in feet ) of the cone,

So, the diameter of the cone = 2 × radius = 2r feet,

∵ The diameter of the base of the cone is three times the height,

If h represents the height of the cone,

⇒ 2r = 3 × h,

⇒ $r=\frac{3h}{2}$ feet,

∵ Volume of a cone,

$V=\frac{1}{3}\pi R^2 H$

Where,

R = radius, H = height,

Thus, the volume of the given cone is,

$V=\frac{1}{3}\pi r^2 h$

$=\frac{1}{3}\pi (\frac{3h}{2})^2 h$

$=\frac{3}{4}\pi h^3$

Differentiating with respect to t ( time )

$\frac{dV}{dt}=\frac{9}{4}\pi h^2\frac{dh}{dt}$

We have,

$\frac{dV}{dt}=6\text{ cubic ft per min},h=2\text{ feet}$

$6=\frac{9}{4}\pi (2)^2 \frac{dh}{dt}$

$6=9\pi \frac{dh}{dt}$

$\implies \frac{dh}{dt}=\frac{6}{9\pi }\approx 0.2122\text{ ft per min}$

4 0

3 years ago

Find the circumference of the circle. Round to the nearest hundredth.

igor_vitrenko [27]

I think it’s A hope this helped

6 0

2 years ago

Which calculation will ALWAYS give a result greater than 1? A.5 × a number less than 1 B.4/9+ a fraction less than 12 C. 1 3/4 -

Bas_tet [7]

Answer:

C. 1 3/4 - (a fraction less than 3/4)

Step-by-step explanation:

Your number sense should be able to help you with this one.

A. 5 × 1/10 = 1/2, not a number greater than 1

B. 4/9 + 1/3 = 7/9, not a number greater than 1

C. 1 3/4 -1/2 = 1 1/4, a number greater than 1 (see below for more explanation)

D. 7/8 × 1/2 = 7/16, not a number greater than 1.

__

More explanation

Let x represent a number less than 3/4. Then we want to make sure that ...

y = 1 3/4 - x

will be greater than 1.

Solving for x, we get ...

x = 1 3/4 - y

Applying the requirement that x < 3/4, we have ...

x < 3/4

(1 3/4 -y) < 3/4

1 3/4 < y + 3/4 . . . . . . add y

1 < y . . . . . . . . . . . . . . .subtract 3/4

We see that the condition on x makes sure that y is always greater than 1.

3 0

3 years ago

Subtract X2 + 8x +9 - (x2 + 4x)