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3 years ago

What is the solution to this system of linear equations? 3x - 2y = 14 5x + y = 32

Mathematics

2 answers:

ratelena [41]3 years ago

4 0

Answer:

x=6 and y=2

Step-by-step explanation:

3x-2y=14 _1st equation

5x+y=32 _2nd equation

Multiplying 2nd equation by two and adding both equation

3x-2y=14

10x+2y=64

_________

13x=78

x=78÷13

x=6

Putting the value of x in 1st equation

3×6-2y=14

18-2y=14

2y=18-14

2y=4

y=4÷2

y=2

Cerrena [4.2K]3 years ago

4 0

Answer: B

Step-by-step explanation:

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Evalueate-2/5-x(-9/10) where x= 4/5

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Answer:

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Step-by-step explanation:

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2 years ago

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A chemical substance has a decay rate of 6.9% per day. The rate of change of an amount N of the chemical is given by the equatio

GaryK [48]

Answer:

a) $N=N_0e^{-0.069t}$

b) $N=696.9$ grams

c) $t=10$ days

Step-by-step explanation:

We are going to use separation of variables to solve.

Get all your t's to one side and your N's to opposing side.

$\frac{dN}{dt}=-0.069N$

Multiply both sides by $dt$ :

$dN=-0.069N dt$

Divided both sides by $N$ :

$\frac{dN}{N}=-0.069 dt$

Integrate both sides:

$\ln|N|=-0.069t+C$

The equivalent exponential form is:

$e^{-0.069t+C}=N$

Using law of exponents you can write this as:

$e^{-0.069t}e^C=N$

$e^C$ is just a positive constant that I'm going to replace with K:

$e^{-0.069t}K=N$

Applying the symmetric property of equality:

$N=e^{-0.069t}K$

Applying the commutative property of multiplication:

$N=Ke^{-0.069t}$

K actually represents the initial amount of chemical substance since when plugging in 0 for t you get K for N, like so:

$N=Ke^{-0.069 \cdot 0}$

$N=Ke^{0}$

$N=K(1)$

$N=K$

We are given at time 0 the amount of chemical substance,N, is K. They want us to represent this value with $N_0$ instead. So the exponential equation is:

$N=N_0e^{-0.069t}$

We are given $N_0=800$ at $t=0$ .

We are asked to find how much of the chemical substance, N, remains after 2 days. So we replace t with 2 in $N=800e^{-0.069t}$ :

$N=800e^{-0.069 \cdot 2}$

Put into calculator:

$N=696.9$ (this was rounded to the nearest tenths)

The last part is asking for how many days will it take a initial 800 grams to go down to half of 800 grams.

We need to see the following equation:

$\frac{1}{2}(800)=800e^{-0.069t}$

$400=800e^{-0.069t}$

Divide both sides by 800:

$\frac{400}{800}=e^{-0.069t}$

Reduce the fraction:

$\frac{1}{2}=e^{-0.069t}$

Convert to logarithmic form:

$\ln(\frac{1}{2})=-0.069t$

Divide both sides by -0.069:

$\frac{\ln(\frac{1}{2})}{-0.069}=t$

Input into calculator:

$10.0=t$

$t=10.0$

$t=10$

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Find the zeros of the polynomial function: <br> f(x) = 9x^3 - 27x^2 - 4x + 12.

hichkok12 [17]

Answer:

{-2/3, 2/3, 3}

Step-by-step explanation:

The equation can be factored by grouping.

f(x) = (9x^3 -27x^2) +(-4x +12)

f(x) = 9x^2(x -3) -4(x -3)

f(x) = (9x^2 -4)(x -3)

We recognize the first factor as the difference of squares, so know it can be further factored to give ...

f(x) = (3x -2)(3x +2)(x -3)

The zeros are the values of x that make these factors be zero:

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The zeros of the polynomial are x = -2/3, 2/3, 3.

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