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3 years ago

Must a function this is decreasing over a given interval always be negative over the same interval? Explain

Mathematics

2 answers:

Westkost [7]3 years ago

8 0

Answer:

For a function to be decreasing over an interval, the outputs on the function are getting smaller as the inputs of the function are getting larger, but the outputs could be positive or negative. For a function to be negative over an interval, the outputs must be negative, while the inputs could be positive or negative.

aleksklad [387]3 years ago

4 0

It is certainly possible for a function decreasing over a certain interval to be negative, but no rule that says it must be. On the other hand, where the function is decreasing, the rate of change of the function must be negative.

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For the following telescoping series, find a formula for the nth term of the sequence of partial sums

gtnhenbr [62]

I'm guessing the sum is supposed to be

$\displaystyle\sum_{k=1}^\infty\frac{10}{(5k-1)(5k+4)}$

Split the summand into partial fractions:

$\dfrac1{(5k-1)(5k+4)}=\dfrac a{5k-1}+\dfrac b{5k+4}$

$1=a(5k+4)+b(5k-1)$

If $k=-\frac45$ , then

$1=b(-4-1)\implies b=-\frac15$

If $k=\frac15$ , then

$1=a(1+4)\implies a=\frac15$

This means

$\dfrac{10}{(5k-1)(5k+4)}=\dfrac2{5k-1}-\dfrac2{5k+4}$

Consider the $n$ th partial sum of the series:

$S_n=2\left(\dfrac14-\dfrac19\right)+2\left(\dfrac19-\dfrac1{14}\right)+2\left(\dfrac1{14}-\dfrac1{19}\right)+\cdots+2\left(\dfrac1{5n-1}-\dfrac1{5n+4}\right)$

The sum telescopes so that

$S_n=\dfrac2{14}-\dfrac2{5n+4}$

and as $n\to\infty$ , the second term vanishes and leaves us with

$\displaystyle\sum_{k=1}^\infty\frac{10}{(5k-1)(5k+4)}=\lim_{n\to\infty}S_n=\frac17$

7 0

3 years ago

Find the vertex form of: y=2x^2-5x+13

Ket [755]

The vertex form of a quadratic function is:

f(x) = a(x - h)² + k

The coordinate (h, k) represents a parabola's vertex.

In order to convert a quadratic function in standard form to the vertex form, we can complete the square.

y = 2x² - 5x + 13

Move the constant, 13, to the other side of the equation by subtracting it from both sides of the equation.

y - 13 = 2x² - 5x

Factor out 2 on the right side of the equation.

y - 13 = 2(x² - 2.5x)

Add (b/2)² to both sides of the equation, but remember that since we factored 2 out on the right side of the equation we have to multiply (b/2)² by 2 again on the left side.

y - 13 + 2(2.5/2)² = 2(x² - 2.5x + (2.5/2)²)

y - 13 + 3.125 = 2(x² - 2.5x + 1.5625)

Add the constants on the left and factor the expression on the right to a perfect square.

y - 9.875 = 2(x - 1.25)²

Now, we need y to be by itself again so add 9.875 back to both sides of the equation to move it back to the right side.

y = 2(x - 1.25)² + 9.875

Vertex: (1.25, 9.875)

Solution: y = 2(x - 1.25)² + 9.875

Or if you prefer fractions

y = 2(x - 5/4)² + 79/8

7 0

3 years ago

Pls show work I need the work. Thx

Ainat [17]

Sorry i can’t quite see the image can you do another one

5 0

2 years ago

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ser-zykov [4K]

Answer:

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Step-by-step explanation:

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8 0

2 years ago

A home store donated a percent of everybody sale to charity. The total sales were $6,550 so the store donated $393. What percent

Andrej [43]

Answer:

Step-by-step explanation:

393/6550=0.06

0.06=6%

5 0

3 years ago