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3 years ago

4(-8x + 5) - (-33x - 26) =

1 answer:

8 0

<h2>4(-8x + 5) - (-33x - 26) =</h2><h2>-32x + 20 + 33x + 26= (distributive)</h2><h2>-32x + 33x + 26 + 20= (combine like terms)</h2><h2> x + 46</h2>

Hope it helps.

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A tank contains 60 kg of salt and 1000 L of water. Pure water enters a tank at the rate 6 L/min. The solution is mixed and drain

MissTica

Answer:

(a) 60 kg; (b) 21.6 kg; (c) 0 kg/L

Step-by-step explanation:

(a) Initial amount of salt in tank

The tank initially contains 60 kg of salt.

(b) Amount of salt after 4.5 h

$\text{Let A = mass of salt after t min}\\\text{and }r_{i} = \text{rate of salt coming into tank}\\\text{and }r_{0} =\text{rate of salt going out of tank}$

(i) Set up an expression for the rate of change of salt concentration.

$\dfrac{\text{d}A}{\text{d}t} = r_{i} - r_{o}\\\\\text{The fresh water is entering with no salt, so}\\ r_{i} = 0\\r_{o} = \dfrac{\text{3 L}}{\text{1 min}} \times \dfrac {A\text{ kg}}{\text{1000 L}} =\dfrac{3A}{1000}\text{ kg/min}\\\\\dfrac{\text{d}A}{\text{d}t} = -0.003A \text{ kg/min}$

(ii) Integrate the expression

$\dfrac{\text{d}A}{\text{d}t} = -0.003A\\\\\dfrac{\text{d}A}{A} = -0.003\text{d}t\\\\\int \dfrac{\text{d}A}{A} = -\int 0.003\text{d}t\\\\\ln A = -0.003t + C$

(iii) Find the constant of integration

$\ln A = -0.003t + C\\\text{At t = 0, A = 60 kg/1000 L = 0.060 kg/L} \\\ln (0.060) = -0.003\times0 + C\\C = \ln(0.060)$

(iv) Solve for A as a function of time.

$\text{The integrated rate expression is}\\\ln A = -0.003t + \ln(0.060)\\\text{Solve for } A\\A = 0.060e^{-0.003t}$

(v) Calculate the amount of salt after 4.5 h

a. Convert hours to minutes

$\text{Time} = \text{4.5 h} \times \dfrac{\text{60 min}}{\text{1h}} = \text{270 min}$

b.Calculate the concentration

$A = 0.060e^{-0.003t} = 0.060e^{-0.003\times270} = 0.060e^{-0.81} = 0.060 \times 0.445 = \text{0.0267 kg/L}$

c. Calculate the volume

The tank has been filling at 6 L/min and draining at 3 L/min, so it is filling at a net rate of 3 L/min.

The volume added in 4.5 h is

$\text{Volume added} = \text{270 min} \times \dfrac{\text{3 L}}{\text{1 min}} = \text{810 L}$

Total volume in tank = 1000 L + 810 L = 1810 L

d. Calculate the mass of salt in the tank

$\text{Mass of salt in tank } = \text{1810 L} \times \dfrac{\text{0.0267 kg}}{\text{1 L}} = \textbf{21.6 kg}$

(c) Concentration at infinite time

$\text{As t $\longrightarrow \, -\infty,\, e^{-\infty} \longrightarrow \, 0$, so A $\longrightarrow \, 0$.}$

This makes sense, because the salt is continuously being flushed out by the fresh water coming in.

The graph below shows how the concentration of salt varies with time.

3 0

3 years ago

Evaluate 10.2x + 9.4y when x=2 and y=3

vekshin1

10.2 x 2 = 20.40
9.4 x 3 = 28.20
Total= 48.60

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3 years ago

Add the following polynomials (2x + 5) + (-1x -4) Answer options: 3x + 9, 3x + 1, 1x + 1, 1x + 9

Leni [432]

Answer:

1x+1

Step-by-step explanation:

just open the parentheses

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3 years ago

A person can see the top of a building at an angle of 65°. The person is standing 50 ft away from

zhannawk [14.2K]

9514 1404 393

Answer:

(b) 112.2 ft

Step-by-step explanation:

The relevant trig relation is ...

Tan = Opposite/Adjacent

For the given geometry, this becomes ...

tan(65°) = (height above eye level)/(50 ft)

Then we have ...

(height above eye level) = (50 ft)tan(65°) = 107.2 ft

Adding the height of eye level will give us the height of the building.

building height = (eye level height) + (height above eye level)

building height = (5 ft) + (107.2 ft)

building height = 112.2 ft

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2 years ago

Write an equation of the line that passes through the given point with the given slope

Inessa05 [86]

Did Yu Ever Find The Answer I got the same question??

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3 years ago