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2 years ago

Please help me with a explanation

Mathematics

1 answer:

blagie [28]2 years ago

3 0

Answer:

x = -3 or x = 3

Step-by-step explanation:

Subtract 9 from both sides.

x^2 - 9 = 0

Factor the left side. There is no common factor of the terms. It is a binomial which is the difference of two squares, so it factors into the product of a sum and a difference.

(x + 3)(x - 3) = 0

Set each factor equal to zero.

x + 3 = 0 or x - 3 = 0

Solve each equation.

x = -3 or x = 3

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A tank contains 10 liters of pure water. Saline solution with a variable concentration 5 grams of salt per liter is pumped into

algol [13]

Answer:

dQ(t)/dt = 20 - 2Q(t)/5 , Q(0) = 0

Step-by-step explanation:

The mass flow rate dQ(t)/dt = mass flowing in - mass flowing out

Since 5 g/L of salt is pumped in at a rate of 4 L/min, the mass flow in is thus 5 g/L × 4 L/min = 20 g/min.

Let Q(t) be the mass present at any time, t. The concentration at any time ,t is thus Q(t)/volume = Q(t)/10. Since water drains at a rate of 4 L/min, the mass flow out is thus, Q(t)/10 g/L × 4 L/min = 2Q(t)/5 g/min.

So, dQ(t)/dt = mass flowing in - mass flowing out

dQ(t)/dt = 20 g/min - 2Q(t)/5 g/min

Since the salt just begins to be pumped in, the initial mass of salt in the tank is zero. So Q(0) = 0

So, the initial value problem is thus

dQ(t)/dt = 20 - 2Q(t)/5 , Q(0) = 0

3 0

2 years ago

An estimated 40% of all people were born after the year 2000. If two people are selected at random from around the world, what a

sukhopar [10]

The chances that NEITHER of these two selected people were born after the year 2000 is 0.36

<h3>How to determine the probability?</h3>

The given parameters are:

Year = 2000

Proportion of people born after 2000, p = 40%

Sample size = 2

The chances that NEITHER of these two selected people were born after the year 2000 is calculated as:

P = (1- p)^2

Substitute the known values in the above equation

P = (1 - 40%)^2

Evaluate the exponent

P = 0.36

Hence, the chances that NEITHER of these two selected people were born after the year 2000 is 0.36

Read more about probability at

brainly.com/question/25870256

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4 0

9 months ago

Find the surface area of the composite solid and round to the nearest tenth. Explain your answer.

Orlov [11]

Well, notice the composite is really just 4 triangles atop sitting on top of 4 rectangles, and all of them area stacked up at the edges.

so, for the rectangle's sides,

front and back are two 6x3 rectangles

left and right are two 6x3 rectangles

the bottom part is a 6x6 rectangle

now, we don't include the 6x6 rectangle that's touching the triangles, because that's inside area, and is not SURFACE area, so we nevermind that one.

now, the triangles are just four triangles with a base of 6, and a height of 4, in red noted there.

so, just get the area of all those rectangles and the triangles, sum them up and that's the surface area of the composite,

$\bf \stackrel{lateral~rectangles}{4(6\cdot 3)}~~+~~\stackrel{bottom~rectangle}{(6\cdot 6)}~~+~~\stackrel{triangles}{4\left( \cfrac{1}{2}(6)(4) \right)}$

7 0

2 years ago

PLZ HELP ME. WILL GIVE BRAINLIEST. THANKYOU!!

____ [38]

Answer:

x = 6

Step-by-step explanation:

Given

3x + 30 + x = 10 + 2x + 5x + 2 , simplify both sides

4x + 30 = 7x + 12 ( subtract 7x from both sides )

- 3x + 30 = 12 ( subtract 30 from both sides )

- 3x = - 18 ( divide both sides by - 3 )

x = 6

6 0

2 years ago

Credit card cash advance borrow: $300 rate: 18% per year time: 6 months-,5 300 6

olga nikolaevna [1]

Answer:

Assuming the question is how much interest you will pay in the given time frame with the given terms.

Step-by-step explanation:

Borrowed $300

18% per yr = 18/12 = 1.5% per month

You borrowed for 6 months so you will end up paying 1.5%*6 =9% in interest

$300*(9% or 0.09) = $27 in interest paid + $300 in principal paid if paid off in 6 months.

Total $327.

If this was an economics class you would also have to factor in the depreciation of the principal amount month to month with minimum payments but I am guessing this is just a basic question so the above answer is correct enough.

7 0

1 year ago