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3 years ago

Pls help me

Mathematics

1 answer:

deff fn [24]3 years ago

7 0

Step-by-step explanation:

the sum of these 2 abgles give you 180°

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A rumor spreads through a small town. Let y ( t ) be the fraction of the population that has heard the rumor at time t and assum

Ivan

Answer:

Differential equation

$\frac{dy}{dt} =ky(1-y)$

Solution

$y=\frac{1}{1+4e^{-0.327t}}$

Value of constant k=0.327 days^(-1)

The rumor reaches 80% at 8.48 days.

Step-by-step explanation:

We know

y(t): proportion of people that heard the rumor

y'(t)=ky(1-y), rate of spread of the rumor

Differential equation

$\frac{dy}{dt} =ky(1-y)$

Solving the differential equation

$\frac{dy}{y(1-y)}=k\cdot dt \\\\\int \frac{dx}{y(1-y)} =k \int dt \\\\-ln(1-\frac{1}{y} )+C_0=kt\\\\1-\frac{1}{y} =Ce^{-kt}\\\\\frac{1}{y} =1-Ce^{-kt}\\\\y=\frac{1}{1-Ce^{-kt}}$

Initial conditions:

$y(0)=0.2\\y(3)=0.4\\\\y(0)=0.2=\frac{1}{1-Ce^0}\\\\1-C=1/0.2\\\\C=1-1/0.2= -4\\\\\\y(3)=0.4=\frac{1}{1+4e^{-3k}} \\\\1+4e^{-3k}=1/0.4\\\\e^{-3k}=(2.5-1)/4=0.375\\\\k=ln(0.375)/(-3)=0.327\\\\\\y=\frac{1}{1+4e^{-0.327t}}$

Value of constant k=0.327 days^(-1)

At what time the rumor reaches 80%?

$y(t)=0.8=\frac{1}{1+4e^{-0.327t}} \\\\1+4e^{-0.327t}=1/0.8=1.25\\\\e^{-0.327t}=(1.25-1)/4=0.0625\\\\t=ln(0.0625)/(-0.327)=8.48$

The rumor reaches 80% at 8.48 days.

8 0

3 years ago

Solve with completing the square method:<br>6x²-7x+2=0 and ax²+bx+c=0

Norma-Jean [14]

$6x ^2-7x+2=0\\ \\ a=6 , \ b = -7 , \ c=2 \\ \\\Delta = b^{2}-4ac = (-7)^{2}-4*6*2=49-48=1 \\ \\x_{1}=\frac{-b-\sqrt{\Delta }}{2a} =\frac{7-\sqrt{1}}{2*6}=\frac{7-1}{12} =\frac{6}{12}= \frac{1}{ 2}\\ \\x_{2}=\frac{-b+\sqrt{\Delta }}{2a} =\frac{7+\sqrt{1}}{2*6}=\frac{7+1}{12} =\frac{8}{12}= \frac{2}{ 3}$

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3 years ago

There are 38 roses, 35 tulips, and 22 lilies. The Commutative

Sever21 [200]

there isnt a list of options given but should be something like

38 + 35 + 22 = 22 + 35 + 38

or maybe

38r + 35t + 22l = 22l + 35t + 38r

it equals 95

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2 years ago

A football is punted and follows a path from the line of scrimmage similar to the quadratic equation: y= -¹⁄₂₀ (x-25)² + 30 wher

cluponka [151]

Do it on a Calculator just type it in

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3 years ago

The length of a rectangle is 4 more than 3 times the width if the perimeter of the rectangle is 18.4 cm what is the area of the

garik1379 [7]

Let's call the width: w

the lenght is then 3w+4 ("4 more than 3 times the width")

and the parameter would be 2(w+3w+4), that is 2*(4w+4), that is 8w+8.

this is also equal to 18.4:

8w+8=18.4
8w=10.4
w=1.3

this is the width, and the lenght is:
4+3*1,3=4+3.9=7.9

and the area is their product:
1.3*7.9=10.27

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3 years ago