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2 years ago

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Brad get an allowance of $16 each week, and his younger sister Samantha gets an allowance of $9 each week. Brad save one-half of

his allowance and Samantha saves two-thirds oh her allowance. Suppose brad started with $0 savings and Samantha started with $40. How many weeks will it take until they have the same amount in savings?

1 answer:

Lyrx [107]2 years ago

6 0

Answer:

160

Step-by-step explanation:

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Evaluate the line integral by the two following methods. xy dx + x2y3 dy C is counterclockwise around the triangle with vertices

nadezda [96]

Answer:

a)

$\frac{2}{3}$

b)

$\frac{2}{3}$

Step-by-step explanation:

a) The first part requires that we use line integral to evaluate directly.

The line integral is

$\int_C xydx + {x}^{2} {y}^{3} dy$

where C is counterclockwise around the triangle with vertices (0, 0), (1, 0), and (1, 2)

The boundary of integration is shown in the attachment.

Our first line integral is

$L_1 = \int_ {(0,0)}^{(1,0)} xydx + {x}^{2} {y}^{3} dy$

The equation of this line is y=0, x varies from 0 to 1.

When we substitute y=0 every becomes zero.

$\therefore \: L_1 =0$

Our second line integral is

$L_2 = \int_ {(1,0)}^{(1,2)} xydx + {x}^{2} {y}^{3} dy$

The equation of this line is:

$x = 0 \implies \: dx = 0$

y varies from 1 to 2.

We substitute the boundary and the values to get:

$L_2 = \int_ {1}^{2}1 \cdot y(0) + {1}^{2} \cdot \: {y}^{3} dy$

$L_2 = \int_ {1}^2 {y}^{3} dy = \frac{8}{3}$

The 3rd line integral is:

$L_3 = \int_ {(1,2)}^{(0,0)} xydx + {x}^{2} {y}^{3} dy$

The equation of this line is

$y = 2x \implies \: dy = 2dx$

x varies from 0 to 1.

We substitute to get:

$L_3 = \int_ {1}^{0} x \cdot \: 2xdx + {x}^{2} {(2x)}^{3}(2 dx)$

$L_3 = \int_ {1}^{0} 8 {x}^{5} + 2 {x}^{2} dx = - 2$

The value of the line integral is

$L = L_1 + L_2 + L_3$

$L = 0 + \frac{8}{3} + - 2 = \frac{2}{3}$

b) The second part requires the use of Green's Theorem to evaluate:

$\int_C xydx + {x}^{2} {y}^{3} dy$

Since C is a closed curve with counterclockwise orientation, we can apply the Green's Theorem.

This is given by:

$\int_C \: Pdx +Q \: dy = \int \int_ R \: Q_y - P_x \: dA$

$\int_C \: xydx + {x}^{2} {y}^{3} \: dy = \int \int_ R \: 3 {x}^{2} {y}^{2} - y \: dA$

We choose our region of integration parallel to the y-axis.

$\int_C \: xydx + {x}^{2} {y}^{3} \: dy = \int_ 0^{1} \int_ 0^{2x} \: 3 {x}^{2} {y}^{2} - y \: dydx$

$\int_C \: xydx + {x}^{2} {y}^{3} \: dy = \int_ 0^{1} \: {x}^{2} {y}^{3} - \frac{1}{2} {y}^{2} |_ 0^{2x} dx$

$\int_C \: xydx + {x}^{2} {y}^{3} \: dy = \int_ 0^{1} \: 8{x}^{5} - 2 {x}^{2} dx = \frac{2}{3}$

8 0

2 years ago

In the box, complete the first 4 steps for graphing the quadratic function given. (Use ^ on the keyboard to indicate an exponent

Vaselesa [24]

Step 1: convert the equation into fhe vertex form

To do you can complete squares:

y = - [x^2 + 4x + 3]

y = - [ (x + 2)^2 - 4 + 3]

y = - [ (x + 2)^2 - 1] = - (x+2)^2 + 1

Then the vertex is (-2, 1)

Now you can drasw the vertex

Step 2: Find the roots (zeros)

y = - [ (x + 2)^2 - 1] = 0

(x + 2)^2 - 1 = 0

(x+2)^2 = 1

(x+2) = (+/-) √1

x + 2 = (+/-1)

x = - 2 +/- 1

x = -1 and x = -3

Now you draw the points (-1,0) , (-3,0)

Step 3: find the interception with the y-axis.

That is y value when x = 0

y = - (0)^2 - 4(0) - 3 = -3

Then draw the point (0, -3)

Step 4: given that the coefficent of x is negative (-1) the parabola is open downward.

So, with those four points: vertex (-2,1), (-1,0), (-3,0) and (0,-3), you can sketch the function.

7 0

2 years ago

The angle Johnny holds his pen on paper creates a linear pair. The measure of one angle is 13x + 7. The

tresset_1 [31]

<h3>The value of x is 4.10</h3>

<em><u>Solution:</u></em>

Given that,

The angle Johnny holds his pen on paper creates a linear pair

Angles in a linear pair are supplementary angles

Two angles are supplementary, when they add up to 180 degrees

The measure of one angle is 13x + 7

The measure of the second angle is one less than twice the first angle

Therefore,

Measure of second angle = twice the first angle - 1

Measure of second angle = 2(13x + 7) - 1

Measure of second angle = 26x + 14 - 1

Measure of second angle = 26x + 13

Therefore,

Measure of first angle + measure of second angle = 180

13x + 7 + 26x + 13 = 180

39x + 20 = 180

39x = 180 - 20

39x = 160

x = 4.1

Thus value of x is 4.10

3 0

2 years ago

The local grocery store will purchase food items and mark them up 115%. If the wholesale price of an item was $3.50, what price

jeyben [28]

Answer: $7.525

Step-by-step explanation:

A markup is an amount that is added to the cost price of an item in order to get a sell price that is used to make a profit.

Cost price= $3.50

Markup = 115% = 115/100 × 3.50

= 1.15 × 3.50

= 4.025

Selling price= Cost price + Markup

= $3.50 + $4.025

= $7.525

A customer will pay $7.525 for the item.

8 0

2 years ago

. If x tan 45° sin 30° = cos 30° tan 30°, then x is equal

Phantasy [73]

Answer:

x = $\frac{\sqrt{3} }{3}$

Step-by-step explanation:

You can either use the unit circle to find your values and then solve for x or plug it into the calc directly to find your answer (don't forget to put your mode on deg!). It is much faster to plug it into your calc. Simply just divide both sides by tan45°cos30° and you should isolate x and find your answer.

5 0

2 years ago