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3 years ago

PLEASE HELP ASAP

1 answer:

3 0

Real numbers are "closed" under addition Integers are "not closed" under division. Irrational numbers are "not closed" under multiplication. Rational numbers are "closed" under subtraction. If an operation is closed under a set of numbers that means that the result of the operation will always be within that same set of numbers. If that's not true, then the operation is not closed. So with that in mind, let's look at the problems. Real numbers are (closed,not closed) under addition * Since a real number plus a real number always results in another real number, then real numbers are closed under addition. So the answer is "closed" Integers are ( closed, not closed) under division. * Let's try this counter example. 1 divided by 2 = 1/2. 1/2 is NOT an integer, therefore integers are not closed under division. The answer is "not closed" Irrational numbers are (closed, not closed) under multiplication. * This is a tricky one. You may give an impulsive answer and say "closed". After all, how could you possibly multiply one non repeating infinite sequence by another and get something rational?. But what's pi multiplied by the reciprocal of pi? Both pi and 1/pi are irrational. Yet when you multiply them together you get 1 which is quite rational. So the answer is "not closed" Rational numbers are ( closed, not closed) under subtraction. * Since rational numbers are all numbers that can be expressed as a fraction consisting on an integer numerator and divisor, we can express subtraction as a/b - c/d = ad/bd - bc/bd = (ad-bc)/bd and since all we're doing is adding, subtracting, and multiplying integers which is closed under those operations, that means that rational numbers are also closed under subtraction. So the answer is "closed".

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Find the Maclaurin series for f(x) using the definition of a Maclaurin series. [Assume that f has a power series expansion. Do n

aliya0001 [1]

Answer:

$f(x)=\sum_{n=1}^{\infty}(-1)^{(n-1)}2^{n}\dfrac{x^n}{n}$

Step-by-step explanation:

The Maclaurin series of a function f(x) is the Taylor series of the function of the series around zero which is given by

$f(x)=f(0)+f^{\prime}(0)x+f^{\prime \prime}(0)\dfrac{x^2}{2!}+ ...+f^{(n)}(0)\dfrac{x^n}{n!}+...$

We first compute the n-th derivative of $f(x)=\ln(1+2x)$ , note that

$f^{\prime}(x)= 2 \cdot (1+2x)^{-1}\\f^{\prime \prime}(x)= 2^2\cdot (-1) \cdot (1+2x)^{-2}\\f^{\prime \prime}(x)= 2^3\cdot (-1)^2\cdot 2 \cdot (1+2x)^{-3}\\...\\\\f^{n}(x)= 2^n\cdot (-1)^{(n-1)}\cdot (n-1)! \cdot (1+2x)^{-n}\\$

Now, if we compute the n-th derivative at 0 we get

$f(0)=\ln(1+2\cdot 0)=\ln(1)=0\\\\f^{\prime}(0)=2 \cdot 1 =2\\\\f^{(2)}(0)=2^{2}\cdot(-1)\\\\f^{(3)}(0)=2^{3}\cdot (-1)^2\cdot 2\\\\...\\\\f^{(n)}(0)=2^n\cdot(-1)^{(n-1)}\cdot (n-1)!$

and so the Maclaurin series for f(x)=ln(1+2x) is given by

$f(x)=0+2x-2^2\dfrac{x^2}{2!}+2^3\cdot 2! \dfrac{x^3}{3!}+...+(-1)^{(n-1)}(n-1)!\cdot 2^n\dfrac{x^n}{n!}+...\\\\= 0 + 2x -2^2 \dfrac{x^2}{2!}+2^3\dfrac{x^3}{3!}+...+(-1)^{(n-1)}2^{n}\dfrac{x^n}{n}+...\\\\=\sum_{n=1}^{\infty}(-1)^{(n-1)}2^n\dfrac{x^n}{n}$

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3 years ago

What are the solutions to the equation? 7x^3=28x

11Alexandr11 [23.1K]

7x³ = 28x is our equation. We want its solutions.

When you have x and different powers, set the whole thing equal to zero.

7x³ = 28x

7x³ - 28x = 0

Now notice there's a common x in both terms. Let's factor it out.

x (7x² - 28) = 0

As 7 is a factor of 7 and 28, it too can be factored out.

x (7) (x² - 4) = 0

We can further factor x² - 4. We want a pair of numbers that multiply to 4 and whose sum is zero. The pairs are 1 and 4, 2 and 2. If we add 2 and -2 we get zero.

x (7) (x - 2) (x + 2) = 0

Now we use the Zero Product Property - if some product multiplies to zero, so do its pieces.

x = 0 -----> so x = 0

7 = 0 -----> no solution

x - 2 = 0 ----> so x = 2 after adding 2 to both sides

x + 2 = 0 ---> so = x - 2 after subtracting 2 to both sides

Thus the solutions are x = 0, x = 2, x = -2.

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2 years ago

What is the volume of the prism below?

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B. 75

First you find the area of the triangle:

(base x height)/2
(3 x 5)/2
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7.5

Then you multiply by the length of the prism (10):

7.5 x 10 = 75

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3 years ago

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Answer:

36.869 or 36.87

Step-by-step explanation:

first, you find which trig function you are using. in this case, tangent.

then, you put calculate the arctan(3/4) which is 36.96989765

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It tells us that:

(-2,4)
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Look at (3,5) ... it tells us that x = 3 and y = 5

So y = 5

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3 years ago