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3 years ago

1.2 solving equations by adding or subtracting ×-32=-18

Mathematics

1 answer:

Zielflug [23.3K]3 years ago

5 0

×-32=-18

Move -32 to the other side

Sign changes from -32 to +32 to get x by itself.

x-32+32=-18+32

x= 14

Answer: x= 14

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Let C(n, k) = the number of k-membered subsets of an n-membered set. Find (a) C(6, k) for k = 0,1,2,...,6 (b) C(7, k) for k = 0,

vladimir1956 [14]

Answer:

(a) $C(6,0) = 1$ , $C(6,1) = 6$ , $C(6,2) = 15$ , $C(6,3) = 20$ , $C(6,4) = 15$ , $C(6,5) = 6$ , $C(6,6) = 1$ .

(b) $C(7,0) = 1$ , $C(7,1) = 7$ , $C(7,2) = 21$ , $C(7,3) = 35$ , $C(7,4) = 35$ , $C(7,5) = 21$ , $C(7,6) = 7$ , $C(7,7)=1$ .

Step-by-step explanation:

In this exercise we only need to recall the formula for C(n,k):

$C(n,k) = \frac{n!}{k!(n-k)!}$

where the symbol $n!$ is the factorial and means

$n! = 1\cdot 2\cdot 3\cdot 4\cdtos (n-1)\cdot n$ .

By convention 0!=1. The most important property of the factorial is $n!=(n-1)!\cdot n$ , for example 3!=1*2*3=6.

(a) The explanations to the solutions is just the calculations.

$C(6,0) = \frac{6!}{0!(6-0)!} = \frac{6!}{6!} = 1$

$C(6,1) = \frac{6!}{1!(6-1)!} = \frac{6!}{5!} = \frac{5!\cdot 6}{5!} = 6$

$C(6,2) = \frac{6!}{2!(6-2)!} = \frac{6!}{2\cdot 4!} = \frac{5!\cdot 6}{2\cdot 4!} = \frac{4!\cdot 5\cdot 6}{2\cdot 4!} = \frac{5\cdot 6}{2} = 15$

$C(6,3) = \frac{6!}{3!(6-3)!} = \frac{6!}{3!\cdot 3!} = \frac{5!\cdot 6}{6\cdot 6} = \frac{5!}{6} = \frac{120}{6} = 20$

$C(6,4) = \frac{6!}{4!(6-4)!} = \frac{6!}{4!\cdot 2!} = frac{5!\cdot 6}{2\cdot 4!} = \frac{4!\cdot 5\cdot 6}{2\cdot 4!} = \frac{5\cdot 6}{2} = 15$

$C(6,5) = \frac{6!}{5!(6-5)!} = \frac{6!}{5!} = \frac{5!\cdot 6}{5!} = 6$

$C(6,6) = \frac{6!}{6!(6-6)!} = \frac{6!}{6!} = 1$ .

(b) The explanations to the solutions is just the calculations.

$C(7,0) = \frac{7!}{0!(7-0)!} = \frac{7!}{7!} = 1$

$C(7,1) = \frac{7!}{1!(7-1)!} = \frac{7!}{6!} = \frac{6!\cdot 7}{6!} = 7$

$C(7,2) = \frac{7!}{2!(7-2)!} = \frac{7!}{2\cdot 5!} = \frac{6!\cdot 7}{2\cdot 5!} = \frac{5!\cdot 6\cdot 7}{2\cdot 5!} = \frac{6\cdot 7}{2} = 21$

$C(7,3) = \frac{7!}{3!(7-3)!} = \frac{7!}{3!\cdot 4!} = \frac{6!\cdot 7}{6\cdot 4!} = \frac{5!\cdot 6\cdot 7}{6\cdot 4!} = \frac{120\cdot 7}{24} = 35$

$C(7,4) = \frac{7!}{4!(7-4)!} = \frac{6!\cdot 7}{4!\cdot 3!} = frac{5!\cdot 6\cdot 7}{4!\cdot 6} = \frac{120\cdot 7}{24} = 35$

$C(7,5) = \frac{7!}{5!(7-2)!} = \frac{7!}{5!\cdot 2!} = 21$

$C(7,6) = \frac{7!}{6!(7-6)!} = \frac{7!}{6!} = \frac{6!\cdot 7}{6!} = 7$

$C(7,7) = \frac{7!}{7!(7-7)!} = \frac{7!}{7!} = 1$

For all the calculations just recall that 4! =24 and 5!=120.

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2 years ago

David is saving $250 to buy a bicycle. He saved $8 each week for 12 weeks. He wants to buy the bicycle in 7 more weeks. How much

Colt1911 [192]

Answer:

Step-by-step explanation:

Amount saved = $8 x 12 weeks

= $96

Amount to save = $250- $96

= $154

Amount per week= 154/7

= $22

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2 years ago

which has a greater effect on the volume - changing the radius by a given amount or changing the height by the same amount/ why?

AURORKA [14]

Assuming we’re talking about a cylinder, whose volume formula is V = pi r^2 h…

It will have a greater effect to change a variable’s value that has a greater power on it.

Changing h from 1 to 2 doubles the volume.
Changing r from 1 to 4 quadruples the volume, because 1^2 = 1 and 2^2 = 4. The effect of the change on r is amplified by the power.

3 0

2 years ago

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Alex is 22 years older than Lana. Four years ago Lana’s age was one-half of Alex’s current age. How old was Alex four years ago?

katen-ka-za [31]

Answer:

Step-by-step explanation

22 divided by 2 is 11

it says four years ago so add 11 and 4 and that equals 15

she is 15 right now. then add 22 which is 37 and subtract 4 which your answer would be 33

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2 years ago

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A refrigerator costs $580 a year to run. A family purchases a new one for $1200 that will save them 22% annually in energy costs

NeTakaya

Answer:

It will take nine years and four months for the refrigerator to pay for itself.

Step-by-step explanation:

The new refrigerator which costs $1200, saves the family 22% annually in energy cost.

Since the old refrigerator costs $580 to run, we want to determine how many years it will take for 22% of $580 per year to make $1200.

22% of $580

= 580 × 0.22

= 127.6

That is, it saved then $127.6 per year.

Now,

$1200/127.6

≈ 9.4

Which means, it will take 9 years and 4 months for the refrigerator to pay for itself.

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2 years ago

1.2 solving equations by adding or subtracting ×-32=-18​

1.2 solving equations by adding or subtracting ×-32=-18