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KatRina [158]
3 years ago
5

Joel bought 8 books. Some books cost $13 each and some cost $17 each. In all, he spent $128. Which system of linear equations re

presents the given situation?
Mathematics
1 answer:
Phantasy [73]3 years ago
4 0
If there are x $13 each books and y $17 each books, then we can build the following equations:
x + y = 8    (or y = 8 - x)
13x + 17y = 128   (or y = 128/17 - 13x/17)
:)
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Prove by mathematical induction that 1+2+3+...+n= n(n+1)/2 please can someone help me with this ASAP. Thanks​
Iteru [2.4K]

Let

P(n):\ 1+2+\ldots+n = \dfrac{n(n+1)}{2}

In order to prove this by induction, we first need to prove the base case, i.e. prove that P(1) is true:

P(1):\ 1 = \dfrac{1\cdot 2}{2}=1

So, the base case is ok. Now, we need to assume P(n) and prove P(n+1).

P(n+1) states that

P(n+1):\ 1+2+\ldots+n+(n+1) = \dfrac{(n+1)(n+2)}{2}=\dfrac{n^2+3n+2}{2}

Since we're assuming P(n), we can substitute the sum of the first n terms with their expression:

\underbrace{1+2+\ldots+n}_{P(n)}+n+1 = \dfrac{n(n+1)}{2}+n+1=\dfrac{n(n+1)+2n+2}{2}=\dfrac{n^2+3n+2}{2}

Which terminates the proof, since we showed that

P(n+1):\ 1+2+\ldots+n+(n+1) =\dfrac{n^2+3n+2}{2}

as required

4 0
3 years ago
Jeremiah received $65 for his birthday and used part of it to buy 3 video games. The games cost the same amount, and he had $14
hram777 [196]

Jeremiah got $65 on birthday and spent some money on 3 video games and was left with $14.

He purchased 3 video games.

Let the cost one one video game be v.

The cost of each video game is same

So the cost of 3 video games is 3v.

Also he is left with $14 after paying for three games.

Hence

3v + 14 = 65

Subtracting 14 from both sides

3v + 14 -14 = 65-14

3v = 51

Dividing by 3 on both sides

v = 51/3

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Hence the cost of each video game is $17

5 0
3 years ago
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Artemon [7]

Answer:

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18/42=9/21=3/7 answer

5 0
2 years ago
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18. You are standing beside the Colorado River, 400 feet
Veseljchak [2.6K]
<h3>Answer: B. 781.6 feet approximately</h3>

=======================================================

Work Shown:

The horizontal portion is 400+166 = 566 feet. Label this as 'a', so a = 566. The vertical side is unknown, so b = x. The hypotenuse is c = 965

Use the pythagorean theorem

a^2+b^2 = c^2

566^2+x^2 = 965^2

x^2 = 965^2 - 566^2

x = sqrt( 965^2 - 566^2 )

x = 781.58108984289 which is approximate

x = 781.6 feet when rounding to one decimal place

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