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konstantin123 [22]
3 years ago
5

Please help! 1 question! 50 points! Show your work!

Mathematics
1 answer:
KatRina [158]3 years ago
7 0

Answer:

  \dfrac{2x}{3a^2}

Step-by-step explanation:

\dfrac{3a^4b}{2x}\cdot\dfrac{4x^2}{9a^6b}=\dfrac{3\cdot 4}{2\cdot 9}a^{4-6}b^{1-1}x^{2-1}=\dfrac{2x}{3a^2}

The applicable rules of exponents are ...

  • (a^b)(a^c) = a^(b+c)
  • a^-b = 1/a^b
You might be interested in
Please do this for me <br><br> I am very lazy
Alexandra [31]

First, let's turn all the numbers into improper fractions so that we can find the answer easier.

-2 \frac{1}{4} = r - \frac{4}{5}

-\frac{9}{4} = r - \frac{4}{5}

Now we have to isolate 'r'.

First, we have to make sure that the variable is on one side and all the numbers are on the other side.

To do this, we have to add \frac{4}{5} to both sides.

In order to do this, we need to ensure that both fractions have a common denominator.

-\frac{9}{4} = r - \frac{4}{5}

Ensure that the denominators are the same:

\frac{45}{20} = r - \frac{16}{20}

\frac{45}{20} + \frac{16}{20} = r

\frac{61}{20} = r

Good luck!

6 0
3 years ago
Prove that
Pani-rosa [81]
Let's start from what we know.

(1)\qquad\sum\limits_{k=1}^n1=\underbrace{1+1+\ldots+1}_{n}=n\cdot 1=n\\\\\\&#10;(2)\qquad\sum\limits_{k=1}^nk=1+2+3+\ldots+n=\dfrac{n(n+1)}{2}\quad\text{(arithmetic  series)}\\\\\\&#10;(3)\qquad\sum\limits_{k=1}^nk\ \textgreater \ 0\quad\implies\quad\left|\sum\limits_{k=1}^nk\right|=\sum\limits_{k=1}^nk

Note that:

\sum\limits_{k=1}^n(-1)^k\cdot k^2=(-1)^1\cdot1^2+(-1)^2\cdot2^2+(-1)^3\cdot3^2+\dots+(-1)^n\cdot n^2=\\\\\\=-1^2+2^2-3^2+4^2-5^2+\dots\pm n^2

(sign of last term will be + when n is even and - when n is odd).
Sum is finite so we can split it into two sums, first S_n^+ with only positive trems (squares of even numbers) and second S_n^- with negative (squares of odd numbers). So:

\sum\limits_{k=1}^n(-1)^k\cdot k^2=S_n^+-S_n^-

And now the proof.

1) n is even.

In this case, both S_n^+ and S_n^- have \dfrac{n}{2} terms. For example if n=8 then:

S_8^+=\underbrace{2^2+4^2+6^2+8^2}_{\frac{8}{2}=4}\qquad\text{(even numbers)}\\\\\\&#10;S_8^-=\underbrace{1^2+3^2+5^2+7^2}_{\frac{8}{2}=4}\qquad\text{(odd numbers)}\\\\\\

Generally, there will be:

S_n^+=\sum\limits_{k=1}^\frac{n}{2}(2k)^2\\\\\\S_n^-=\sum\limits_{k=1}^\frac{n}{2}(2k-1)^2\\\\\\

Now, calculate our sum:

\left|\sum\limits_{k=1}^n(-1)^k\cdot k^2\right|=\left|S_n^+-S_n^-\right|=&#10;\left|\sum\limits_{k=1}^\frac{n}{2}(2k)^2-\sum\limits_{k=1}^\frac{n}{2}(2k-1)^2\right|=\\\\\\=&#10;\left|\sum\limits_{k=1}^\frac{n}{2}4k^2-\sum\limits_{k=1}^\frac{n}{2}\left(4k^2-4k+1\right)\right|=\\\\\\

=\left|4\sum\limits_{k=1}^\frac{n}{2}k^2-4\sum\limits_{k=1}^\frac{n}{2}k^2+4\sum\limits_{k=1}^\frac{n}{2}k-\sum\limits_{k=1}^\frac{n}{2}1\right|=\left|4\sum\limits_{k=1}^\frac{n}{2}k-\sum\limits_{k=1}^\frac{n}{2}1\right|\stackrel{(1),(2)}{=}\\\\\\=&#10;\left|4\dfrac{\frac{n}{2}(\frac{n}{2}+1)}{2}-\dfrac{n}{2}\right|=\left|2\cdot\dfrac{n}{2}\left(\dfrac{n}{2}+1\right)-\dfrac{n}{2}\right|=\left|n\left(\dfrac{n}{2}+1\right)-\dfrac{n}{2}\right|=\\\\\\&#10;

=\left|\dfrac{n^2}{2}+n-\dfrac{n}{2}\right|=\left|\dfrac{n^2}{2}+\dfrac{n}{2}\right|=\left|\dfrac{n^2+n}{2}\right|=\left|\dfrac{n(n+1)}{2}\right|\stackrel{(2)}{=}\\\\\\\stackrel{(2)}{=}&#10;\left|\sum\limits_{k=1}^nk\right|\stackrel{(3)}{=}\sum\limits_{k=1}^nk

So in this case we prove, that:

 \left|\sum\limits_{k=1}^n(-1)^k\cdot k^2\right|=\sum\limits_{k=1}^nk

2) n is odd.

Here, S_n^- has more terms than S_n^+. For example if n=7 then:

S_7^-=\underbrace{1^2+3^2+5^2+7^2}_{\frac{n+1}{2}=\frac{7+1}{2}=4}\\\\\\&#10;S_7^+=\underbrace{2^2+4^4+6^2}_{\frac{n+1}{2}-1=\frac{7+1}{2}-1=3}\\\\\\

So there is \dfrac{n+1}{2} terms in S_n^-, \dfrac{n+1}{2}-1 terms in S_n^+ and:

S_n^+=\sum\limits_{k=1}^{\frac{n+1}{2}-1}(2k)^2\\\\\\&#10;S_n^-=\sum\limits_{k=1}^{\frac{n+1}{2}}(2k-1)^2

Now, we can calculate our sum:

\left|\sum\limits_{k=1}^n(-1)^k\cdot k^2\right|=\left|S_n^+-S_n^-\right|=&#10;\left|\sum\limits_{k=1}^{\frac{n+1}{2}-1}(2k)^2-\sum\limits_{k=1}^{\frac{n+1}{2}}(2k-1)^2\right|=\\\\\\=&#10;\left|\sum\limits_{k=1}^{\frac{n+1}{2}-1}4k^2-\sum\limits_{k=1}^{\frac{n+1}{2}}\left(4k^2-4k+1\right)\right|=\\\\\\=&#10;\left|\sum\limits_{k=1}^{\frac{n-1}{2}-1}4k^2-\sum\limits_{k=1}^{\frac{n+1}{2}}4k^2+\sum\limits_{k=1}^{\frac{n+1}{2}}4k-\sum\limits_{k=1}^{\frac{n+1}{2}}1\right|=\\\\\\

=\left|\sum\limits_{k=1}^{\frac{n-1}{2}-1}4k^2-\sum\limits_{k=1}^{\frac{n+1}{2}-1}4k^2-4\left(\dfrac{n+1}{2}\right)^2+\sum\limits_{k=1}^{\frac{n+1}{2}}4k-\sum\limits_{k=1}^{\frac{n+1}{2}}1\right|=\\\\\\=&#10;\left|-4\left(\dfrac{n+1}{2}\right)^2+4\sum\limits_{k=1}^{\frac{n+1}{2}}k-\sum\limits_{k=1}^{\frac{n+1}{2}}1\right|\stackrel{(1),(2)}{=}\\\\\\&#10;\stackrel{(1),(2)}{=}\left|-4\dfrac{n^2+2n+1}{4}+4\dfrac{\frac{n+1}{2}\left(\frac{n+1}{2}+1\right)}{2}-\dfrac{n+1}{2}\right|=\\\\\\

=\left|-n^2-2n-1+2\cdot\dfrac{n+1}{2}\left(\dfrac{n+1}{2}+1\right)-\dfrac{n+1}{2}\right|=\\\\\\=&#10;\left|-n^2-2n-1+(n+1)\left(\dfrac{n+1}{2}+1\right)-\dfrac{n+1}{2}\right|=\\\\\\=&#10;\left|-n^2-2n-1+\dfrac{(n+1)^2}{2}+n+1-\dfrac{n+1}{2}\right|=\\\\\\=&#10;\left|-n^2-n+\dfrac{n^2+2n+1}{2}-\dfrac{n+1}{2}\right|=\\\\\\=&#10;\left|-n^2-n+\dfrac{n^2}{2}+n+\dfrac{1}{2}-\dfrac{n}{2}-\dfrac{1}{2}\right|=\left|-\dfrac{n^2}{2}-\dfrac{n}{2}\right|=\left|-\dfrac{n^2+n}{2}\right|=\\\\\\

=\left|-\dfrac{n(n+1)}{2}\right|=|-1|\cdot\left|\dfrac{n(n+1)}{2}\right|=\left|\dfrac{n(n+1)}{2}\right|\stackrel{(2)}{=}\left|\sum\limits_{k=1}^nk\right|\stackrel{(3)}{=}\sum\limits_{k=1}^nk

We consider all possible n so we prove that:

\forall_{n\in\mathbb{N}}\quad\left|\sum\limits_{k=1}^n(-1)^k\cdot k^2\right|=\sum\limits_{k=1}^nk
7 0
3 years ago
Help me pls 20 POINTS
Tema [17]

Answer:

bottom =80m^2

Side =50m^2

triangle = 3 ×8 ×5

6 0
2 years ago
Determine the slope of the line represented by y = 2x - 9
lbvjy [14]

Answer:

2

Step-by-step explanation:

2x is the slope which is just 2

7 0
3 years ago
Aziza has a triangle with two sides measuring 11 in. and 15 in. She claims that the third side can be any length as long as it i
irina [24]

Answer:

Aziza’s claim is incomplete. The third side must be between 4 in. and 26 in.

Step-by-step explanation:

With the Triangle Inequality Theorem, saying that the sum of lengths of any two sides of a triangle is greater than the length of the third side. With this we can develop two inequalities:

11 + 15 > x

26 > x

rewrite this as x < 26

11 + x > 15

x > 15 - 11   Subtract 11 from both sides

x > 4

Therefore, the third side can be anywhere greater than 4 inches and less than and less than 26 inches.

4 <  x < 26

4 0
3 years ago
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