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2 years ago

30 POINTS!!!!!

Mathematics

1 answer:

Whitepunk [10]2 years ago

8 0

Answer:

A third group that does not use a cell phone before bedtime

Step-by-step explanation:

Both groups have the use of a cellphone before bedtime, and the amount used would affect their time to fall asleep, but another group is needed that doesn't use a cellphone to calculate the effect of it not being used and seeing the results.

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03,

Nataly_w [17]

Answer:

x = 5

Step-by-step explanation:

(7x + 16) = 90 - 39

7x + 16 = 51

7x = 51 - 16 = 35

x = 5

6 0

3 years ago

Read 2 more answers

3/5 of 7 pls help shshshshs

vaieri [72.5K]

Answer:

11.6666666667

Step-by-step explanation:

First you multiply 7 by 5

7x5=35

Then you divide 35 by 3

35/3 = 11.6666666667

4 0

2 years ago

Save me the headache

maxonik [38]

$(9\sin2x+9\cos2x)^2=81$

Taking the square root of both sides gives two possible cases,

$9\sin2x+9\cos2x=9\implies\sin2x+\cos2x=1$

$9\sin2x+9\cos2x=-9\implies\sin2x+\cos2x=-1$

Recall that

$\sin(\alpha\pm\beta)=\sin\alpha\cos\beta\pm\cos\alpha\sin\beta$

If $\alpha=2x$ and $\beta=\dfrac\pi4$ , we have

$\sin\left(2x+\dfrac\pi4\right)=\dfrac{\sin2x+\cos2x}{\sqrt2}$

so in the equations above, we can write

$\sin2x+\cos2x=\sqrt2\sin\left(2x+\dfrac\pi4\right)=\pm1$

Then in the first case,

$\sqrt2\sin\left(2x+\dfrac\pi4\right)=1\implies\sin\left(2x+\dfrac\pi4\right)=\dfrac1{\sqrt2}$

$\implies2x+\dfrac\pi4=\dfrac\pi4+2n\pi\text{ or }\dfrac{3\pi}4+2n\pi$

(where $n$ is any integer)

$\implies2x=2n\pi\text{ or }\dfrac\pi2+2n\pi$

$\implies x=n\pi\text{ or }\dfrac\pi4+n\pi$

and in the second,

$\sqrt2\sin\left(2x+\dfrac\pi4\right)=-1\implies\sin\left(2x+\dfrac\pi4\right)=-\dfrac1{\sqrt2}$

$\implies2x+\dfrac\pi4=-\dfrac\pi4+2n\pi\text{ or }-\dfrac{3\pi}4+2n\pi$

$\implies2x=-\dfrac\pi2+2n\pi\text{ or }-\pi+2n\pi$

$\implies x=-\dfrac\pi4+n\pi\text{ or }-\dfrac\pi2+n\pi$

Then the solutions that fall in the interval $[0,2\pi)$ are

$x=0,\dfrac\pi4,\dfrac\pi2,\dfrac{3\pi}4,\pi,\dfrac{5\pi}4,\dfrac{3\pi}2,\dfrac{7\pi}4$

5 0

3 years ago

Read 2 more answers

Help please!! <br> What is the domain of the function shown in the graph?

diamong [38]

Answer:

x ≥ - 1

Step-by-step explanation:

4 0

3 years ago

Find the product of 0.51 x 2.427

Natalka [10]

Answer:1.23777

Step-by-step explanation: Calculators answer

7 0

1 year ago