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2 years ago

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Challenge A cell phone plan costs $19.80 per month for 400 minutes of talk time. It costs an additional $0.06 per minute for eac

h minute over 400 minutes. To get e-mail access, it costs 20% of the price for 400 minutes of talk time. Your bill, which includes e-mail, is the same each month for 6 months. The total cost for all 6 months is $168.48, Write and solve an equation to find the number of minutes of talk time you use each month.

1 answer:

dimaraw [331]2 years ago

8 0

Answer:

2,541 minutes

Step-by-step explanation:

i hope this helps

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Solve the following equations: (a) x^11=13 mod 35 (b) x^5=3 mod 64

tino4ka555 [31]

a.

$x^{11}=13\pmod{35}\implies\begin{cases}x^{11}\equiv13\equiv3\pmod5\\x^{11}\equiv13\equiv6\pmod7\end{cases}$

By Fermat's little theorem, we have

$x^{11}\equiv (x^5)^2x\equiv x^3\equiv3\pmod5$

$x^{11}\equiv x^7x^4\equiv x^5\equiv6\pmod 7$

5 and 7 are both prime, so $\varphi(5)=4$ and $\varphi(7)=6$ . By Euler's theorem, we get

$x^4\equiv1\pmod5\implies x\equiv3^{-1}\equiv2\pmod5$

$x^6\equiv1\pmod7\impleis x\equiv6^{-1}\equiv6\pmod7$

Now we can use the Chinese remainder theorem to solve for $x$ . Start with

$x=2\cdot7+5\cdot6$

Taken mod 5, the second term vanishes and $14\equiv4\pmod5$ . Multiply by the inverse of 4 mod 5 (4), then by 2.

$x=2\cdot7\cdot4\cdot2+5\cdot6$

Taken mod 7, the first term vanishes and $30\equiv2\pmod7$ . Multiply by the inverse of 2 mod 7 (4), then by 6.

$x=2\cdot7\cdot4\cdot2+5\cdot6\cdot4\cdot6$

$\implies x\equiv832\pmod{5\cdot7}\implies\boxed{x\equiv27\pmod{35}}$

b.

$x^5\equiv3\pmod{64}$

We have $\varphi(64)=32$ , so by Euler's theorem,

$x^{32}\equiv1\pmod{64}$

Now, raising both sides of the original congruence to the power of 6 gives

$x^{30}\equiv3^6\equiv729\equiv25\pmod{64}$

Then multiplying both sides by $x^2$ gives

$x^{32}\equiv25x^2\equiv1\pmod{64}$

so that $x^2$ is the inverse of 25 mod 64. To find this inverse, solve for $y$ in $25y\equiv1\pmod{64}$ . Using the Euclidean algorithm, we have

64 = 2*25 + 14

25 = 1*14 + 11

14 = 1*11 + 3

11 = 3*3 + 2

3 = 1*2 + 1

=> 1 = 9*64 - 23*25

so that $(-23)\cdot25\equiv1\pmod{64}\implies y=25^{-1}\equiv-23\equiv41\pmod{64}$ .

So we know

$25x^2\equiv1\pmod{64}\implies x^2\equiv41\pmod{64}$

Squaring both sides of this gives

$x^4\equiv1681\equiv17\pmod{64}$

and multiplying both sides by $x$ tells us

$x^5\equiv17x\equiv3\pmod{64}$

Use the Euclidean algorithm to solve for $x$ .

64 = 3*17 + 13

17 = 1*13 + 4

13 = 3*4 + 1

=> 1 = 4*64 - 15*17

so that $(-15)\cdot17\equiv1\pmod{64}\implies17^{-1}\equiv-15\equiv49\pmod{64}$ , and so $x\equiv147\pmod{64}\implies\boxed{x\equiv19\pmod{64}}$

5 0

2 years ago

Johnathan ran 5 days this week. The most he ran in one day was 3.5 miles. Write an inequality that shows the distance johnathan

Mekhanik [1.2K]

<em><u>An inequality that shows the distance Johnathan could of ran any day this week is:</u></em>

$x\leq 3.5$

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

Let "x" be the distance Johnathan can run any day of this week

Given that,

Johnathan ran 5 days this week. The most he ran in one day was 3.5 miles

Therefore,

Number of days ran = 5

The most he ran in 1 day = 3.5 miles

Thus, the maximum distance he ran in a week is given as:

$distance = 5 \times 3.5 = 17.5$

The maximum distance he ran in a week is 17.5 miles

If we let x be the distance he can run any day of this week then, we get a inequality as:

$x\leq 3.5$

If we let y be the total distance he can travel in a week then, we may express it as,

$y\leq 17.5$

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2 years ago

write the slope-intercept form of the line with a slope of 2 and a y-intercept of -4. include your work in your final answer.

IgorLugansk [536]

I cant really show you how to graph this but i can try to explain it. you would make a 4 quadrant graph and do rise over run.
1)start by making the graph
2) on the line of the graph marked Y is where you would put -4
3) From -4, you would go up (rise) by 2 and go over to the right 1 where you end is the slop

5 0

3 years ago

Solve the Quadratic Equation.

vichka [17]

Answer:

x = ± 2i

Step-by-step explanation:

The equation has no real roots, gut has complex roots

Given

x² = - 4 ( take the square root of both sides )

x = ± $\sqrt{-4}$

= ± $\sqrt{4(-1)}$

[ Note that $\sqrt{-1}$ = i ]

= ± $\sqrt{4}$ × $\sqrt{-1}$ = ± 2i

7 0

3 years ago

balu736 [363]

DI’m pretty sure it’s

6 0

2 years ago