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3 years ago

9

double the number plus three times another number is 54. the difference between these two numbers is three. what are the two num

bers?

1 answer:

DerKrebs [107]3 years ago

3 0

Step-by-step explanation:

54

=2×27

=54

=27×2

=54

=2,27

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Really need the answer, I will give brainlist!!!!

djverab [1.8K]

Answer:

The speed of the boat is 29 km/h and the speed of the stream is 19 km/h.

Step-by-step explanation:

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3 years ago

Find the vertex of the graph of f(x)=-4(x-1)(x+5)

madreJ [45]

The vertex of the graph is (h, k) = (- 2, 36).

<h3>How to find analytically the vertex of a quadratic equation</h3>

In this question we have a quadratic equation of the form f(x) = a · (x - r₁) · (x - r₂) and we need to transform the expression into its vertex form of determine the coordinates of the vertex. First, we need to exprand the expression:

f(x) = - 4 · (x - 1) · (x + 5)

f(x) = - 4 · (x² + 4 · x - 5)

f(x) = - 4 · x² - 16 · x + 20

Now we proceed to complete the square:

f(x) = - (4 · x² + 16 · x - 20)

- f(x) = 4 · x² + 16 · x - 20

- f(x) = (2 · x)² + 8 · (2 · x) - 20

- f(x) + 36 = (2 · x)² + 8 · (2 · x) + 16

- f(x) + 36 = (2 · x + 4)²

- f(x) + 36 = 4 · (x + 2)²

f(x) - 36 = - 4 · (x + 2)²

The vertex of the graph is (h, k) = (- 2, 36).

To learn more on quadratic equations: brainly.com/question/17177510

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1 year ago

Initially 100 milligrams of a radioactive substance was present. After 6 hours the mass had decreased by 3%. If the rate of deca

Hitman42 [59]

Answer:

The half-life of the radioactive substance is 135.9 hours.

Step-by-step explanation:

The rate of decay is proportional to the amount of the substance present at time t

This means that the amount of the substance can be modeled by the following differential equation:

$\frac{dQ}{dt} = -rt$

Which has the following solution:

$Q(t) = Q(0)e^{-rt}$

In which Q(t) is the amount after t hours, Q(0) is the initial amount and r is the decay rate.

After 6 hours the mass had decreased by 3%.

This means that $Q(6) = (1-0.03)Q(0) = 0.97Q(0)$ . We use this to find r.

$Q(t) = Q(0)e^{-rt}$

$0.97Q(0) = Q(0)e^{-6r}$

$e^{-6r} = 0.97$

$\ln{e^{-6r}} = \ln{0.97}$

$-6r = \ln{0.97}$

$r = -\frac{\ln{0.97}}{6}$

$r = 0.0051$

So

$Q(t) = Q(0)e^{-0.0051t}$

Determine the half-life of the radioactive substance.

This is t for which Q(t) = 0.5Q(0). So

$Q(t) = Q(0)e^{-0.0051t}$

$0.5Q(0) = Q(0)e^{-0.0051t}$

$e^{-0.0051t} = 0.5$

$\ln{e^{-0.0051t}} = \ln{0.5}$

$-0.0051t = \ln{0.5}$

$t = -\frac{\ln{0.5}}{0.0051}$

$t = 135.9$

The half-life of the radioactive substance is 135.9 hours.

6 0

3 years ago

Please help I will brainlist

tamaranim1 [39]

Answer:

C is what i think would be the perimeters of the squares.

Step-by-step explanation:

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2 years ago

Evaluate f(x)=x+6 when x=−2,0, and 5.

ella [17]

Answer:

1. 4

2. 6

3. 11

Step-by-step explanation:

Plug each number into the equation (in place of x) to get the answer.

1. f(-2) = -2+6 = 4

2. f(0) = 0+6 = 6

3. f(5) = 5+6 = 11

6 0

3 years ago