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3 years ago

Solve for x. 2x+3y=20 -2x+y=4

Mathematics

1 answer:

Mama L [17]3 years ago

3 0

Answer:

x = 1

Step-by-step explanation:

-2x + y = 4

y = 2x + 4

2x + 3y = 20

2x + 3(2x + 4) = 20

2x + 6x + 12 = 20

8x + 12 = 20

8x = 8

x = 1

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A mass weighing 16 pounds stretches a spring (8/3) feet. The mass is initially released from rest from a point 2 feet below the

mezya [45]

Answer with Step-by-step explanation:

Let a mass weighing 16 pounds stretches a spring $\frac{8}{3}$ feet.

Mass= $m=\frac{W}{g}$

Mass= $m=\frac{16}{32}$

$g=32 ft/s^2$

Mass,m= $\frac{1}{2}$ Slug

By hook's law

$w=kx$

$16=\frac{8}{3} k$

$k=\frac{16\times 3}{8}=6 lb/ft$

$f(t)=10cos(3t)$

A damping force is numerically equal to 1/2 the instantaneous velocity

$\beta=\frac{1}{2}$

Equation of motion :

$m\frac{d^2x}{dt^2}=-kx-\beta \frac{dx}{dt}+f(t)$

Using this equation

$\frac{1}{2}\frac{d^2x}{dt^2}=-6x-\frac{1}{2}\frac{dx}{dt}+10cos(3t)$

$\frac{1}{2}\frac{d^2x}{dt^2}+\frac{1}{2}\frac{dx}{dt}+6x=10cos(3t)$

$\frac{d^2x}{dt^2}+\frac{dx}{dt}+12x=20cos(3t)$

Auxillary equation

$m^2+m+12=0$

$m=\frac{-1\pm\sqrt{1-4(1)(12)}}{2}$

$m=\frac{-1\pmi\sqrt{47}}{2}$

$m_1=\frac{-1+i\sqrt{47}}{2}$

$m_2=\frac{-1-i\sqrt{47}}{2}$

Complementary function

$e^{\frac{-t}{2}}(c_1cos\frac{\sqrt{47}}{2}+c_2sin\frac{\sqrt{47}}{2})$

To find the particular solution using undetermined coefficient method

$x_p(t)=Acos(3t)+Bsin(3t)$

$x'_p(t)=-3Asin(3t)+3Bcos(3t)$

$x''_p(t)=-9Acos(3t)-9sin(3t)$

This solution satisfied the equation therefore, substitute the values in the differential equation

$-9Acos(3t)-9Bsin(3t)-3Asin(3t)+3Bcos(3t)+12(Acos(3t)+Bsin(3t))=20cos(3t)$

$(3B+3A)cos(3t)+(3B-3A)sin(3t)=20cso(3t)$

Comparing on both sides

$3B+3A=20$

$3B-3A=0$

Adding both equation then, we get

$6B=20$

$B=\frac{20}{6}=\frac{10}{3}$

Substitute the value of B in any equation

$3A+10=20$

$3A=20-10=10$

$A=\frac{10}{3}$

Particular solution, $x_p(t)=\frac{10}{3}cos(3t)+\frac{10}{3}sin(3t)$

Now, the general solution

$x(t)=e^{-\frac{t}{2}}(c_1cos(\frac{\sqrt{47}t}{2})+c_2sin(\frac{\sqrt{47}t}{2})+\frac{10}{3}cos(3t)+\frac{10}{3}sin(3t)$

From initial condition

x(0)=2 ft

x'(0)=0

Substitute the values t=0 and x(0)=2

$2=c_1+\frac{10}{3}$

$2-\frac{10}{3}=c_1$

$c_1=\frac{-4}{3}$

$x'(t)=-\frac{1}{2}e^{-\frac{t}{2}}(c_1cos(\frac{\sqrt{47}t}{2})+c_2sin(\frac{\sqrt{47}t}{2})+e^{-\frac{t}{2}}(-c_1\frac{\sqrt{47}}{2}sin(\frac{\sqrt{47}t}{2})+\frac{\sqrt{47}}{2}c_2cos(\frac{\sqrt{47}t}{2})-10sin(3t)+10cos(3t)$

Substitute x'(0)=0

$0=-\frac{1}{2}\times c_1+10+\frac{\sqrt{47}}{2}c_2$

$\frac{\sqrt{47}}{2}c_2-\frac{1}{2}\times \frac{-4}{3}+10=0$

$\frac{\sqrt{47}}{2}c_2=-\frac{2}{3}-10=-\frac{32}{3}$

$c_2==-\frac{64}{3\sqrt{47}}$

Substitute the values then we get

$x(t)=e^{-\frac{t}{2}}(-\frac{4}{3}cos(\frac{\sqrt{47}t}{2})-\frac{64}{3\sqrt{47}}sin(\frac{\sqrt{47}t}{2})+\frac{10}{3}cos(3t)+\frac{10}{3}sin(3t)$

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3 years ago

Y= 3x+7 y = -2x - 3 Whats the x and y for the solution

Tanzania [10]

Answer:

x=-2, y=1

Step-by-step explanation:

y=3x+7

y=-2x+3

Set the two equations equal to each other:

3x+7=-2x-3

Add 2x to both sides:

5x+7=-3

Subtract 7 from both sides:

5x=-10

Divide both sides by 5:

x=-2

Plug back into one of the original equations to find y:

y=3(-2)+7=-15+7=1

Hope this helps!

8 0

3 years ago

A fair, twenty-faced die has $19$ of its faces numbered from $1$ through $19$ and has one blank face. another fair, twenty-faced

lawyer [7]

Represent 24 as a sum of two numbers, first number from first die and second number from second die.
24=19+5=18+6=17+7=16+8=14+10=13+11=12+12=11+13=10+14=9+15=8+16=7+17=6+18=5+19=4+20 (the sums 15+9 and 20+4 are absent, because there aren't numbers: 20 on the first die and number 9 on the second die). Totally, you receive 15 different representations of 24.
The probability that the sum of the two numbers facing up will be 24 is

 $P= \frac{15}{20\cdot 20} = \frac{3}{80}$ (here $20\cdot 20$ means that you have 20 possibilities to roll first number or blank face on the first die and 20 possibilities to roll number or blank face on the second die).

8 0

3 years ago

PLEASE HELP. WILL GIVE BRAINLIEST

KengaRu [80]

Answer:

x-intercepts = 1,2, and 4, y-intercept = -8

Step-by-step explanation:

x^3 - 7x^2 - 14x - 8 in factored form is equal to (x-1)(x-2)(x-4).

Solving for x-intercepts:

We are actually able to solve for all x-intercepts without the given factor. But since we are given one of the factors, our job becomes much easier.
Using synthetic division, or long division, we factor out the x-intercept 4. Which leaves us with the polynomial x^2 - 3x + 2.
From here we can separate the polynomial into two binomials.
x^2 - 3x + 2 = (x-1)(x-2). Giving us all 3 x-intercepts.
Using Descartes' rules we can identify before even starting the problem how many real x-intercepts there are (Not needed for this problem).

Solving for y-intercept:

The y-intercept is always the coefficient that does not have any assigned x-variables.
The coefficient is -8, thus the y-intercept.
If unsure of the y-intercept, you can always plug in x = 0. Solving for the y-intercept will give you the value of f(0).
If there is no coefficient, the y-intercept is equal to zero.

4 0

3 years ago

Does this table represent a function? Why or why not?

nordsb [41]

no the x and y axis both have repeating numbers

8 0

3 years ago