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3 years ago

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Danielle has her finals coming up and she's worried she'll fail her class. Her past 3 test grades were a 72. an 85, and a 68. Sh

e needs a 70 to pass the class. What grade does she need to make on the final to get a 70?

1 answer:

natka813 [3]3 years ago

7 0

Answer:

55

Step-by-step explanation:

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Which of the following functions are solutions of the differential equation y'' + y = 3 sin x? (select all that apply)

DiKsa [7]

Answer:

C

Step-by-step explanation:

We must compute the derivatives and check if the equation is satisfied.

A. $y'=(3\sin x)'=3\cos x$ . Differentiate again to get $y''=(3\cos x)'=-3\sin x$ , then $y''+y=-3\sin x+3\sin x=0\neq 3\sin x$ so this choice of y doesn't solve the equation.

B. $y'=3\sin x+3x\cos x-5\cosx +5x\sin x=(5x+3)\sin x+(3x-5)\cos x$ and $y''=5\sin x+(5x+3)\cos x+3\cos x-(3x-5)\sin x=(10-3x)\sin x+(5x+6)\cos x$ , then $y''+y=10\sin x+6\cos x\neq 3\sin x$ so y is not a solution

C. $y'=\frac{-3}{2}\cos x+\frac{3}{2}x\sin x$ hence $y''=\frac{3}{2}\sin x+\frac{3}{2}\sin x+\frac{3}{2}x\cos x=3\sin x+\frac{3}{2}x\cos x$ . Then $y''+y=3\sin x+\frac{3}{2}x\cos x-\frac{3}{2}x\cos x=3\sin x$ so y is a solution.

D. $y'=-3\sin x$ and $y''=-3\cos x$ , then $y''+y=0$ thus y isn't a solution

E. $y'=\frac{3}{2}\sin x+\frac{3}{2}x\cos x$ hence $y''=\frac{3}{2}\cos x+\frac{3}{2}\cos x-\frac{3}{2}x\sin x=3\cos x-\frac{3}{2}x\cos x$ . Then $y''+y=3\cos x-\frac{3}{2}x\cos x-\frac{3}{2}x\cos x=3\cos x\neq 3\sin x$ then y is not a solution.

3 0

3 years ago

If you double the radius of a circle, then you will quadruple the circumference of the circle

alexira [117]

Answer:

False

Step-by-step explanation:

No options is attached to the question. However, I'll assume it's a true or false question.

Represent the radius with r.

The circumference is calculated as:

X = 2πr

When the radius is doubled, the new radius R is

R = 2r

And the new circumference, C is:

C = 2πR

Substitute 2r for R

C = 2π * 2r

C = 4πr

Factorize the above equation.

C = 2 * 2πr

Recall X = 2πr;

The expression becomes:

C = 2 * X

C = 2X

This means that the circumference is doubled, not quadrupled.

Hence, the statement is false.

7 0

3 years ago

Help solve this problem please

grigory [225]

Change the left side to improper fractions.

9
--
4
====
3
--
2

Now use the fraction rule. Invert the denominator and multiply that by the numerator.

9 2
== * ==
4 3

18/12 = 3/2 which for now is left alone.

Now work with the fraction on the right side.
1 5/6 = 11/6

Now equate the two results
27/8 = 11/6 // x/1

Simplify the right side
3/2 = 11/6 * 1 / x Remember to invert and multiply that's why you need the 1 underneath the x
3/2 = 11/6x Cross multiply
3* 6x = 11 * 2
18 x = 22
18 x = 22
x = 11/9
x = 1.2222

What are the choices or are there any? The other choice is x = 1.2222

x = 22/18 or
x = 1.22222222 or
x = 11/9

All three are possible and all three are correct and all three are equal. Since I do not have choices, I don't know which one will be acceptable.

Check
I'll do this in decimals. It is much easier.
2.25/1.5 = 1.83333333 / 1.22222222
1.5 = 1.5 so these numbers do check.

4 0

3 years ago

Hey guys! Remember, correct answer gets top! Please don't spam just for the points. That's a cowards move and I will try to dele

notka56 [123]

Answer:

Step 4 7 + (negative 2) = 2 Error

Step-by-step explanation:

Start with 7 positive tiles

Then add 2 negative tiles

Circle 2 positive and 2 negative tiles

We are left with 5 tiles

3 0

3 years ago

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On a road trip you drove 280 miles in 4 hours. a) What is your speed in miles per hour? b) Use your equation to determine how fa

frozen [14]

Answer:

a. 70 miles per hour

b. 840 miles

Step-by-step explanation:

280/4 = 70 miles per hour

70*12 = 840 miles

5 0

3 years ago

Read 2 more answers