1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
e-lub [12.9K]
3 years ago
10

The seventh term of an arithmetic progression is equal to twice the fifth term. The sum

Mathematics
1 answer:
mario62 [17]3 years ago
6 0

Answer:

a₁ = - 24

Step-by-step explanation:

The n th term of an AP is

a_{n} = a₁ + (n - 1)d

where a₁ is the first term and d the common difference

Given a₇ = 2a₅ , then

a₁ + 6d = 2(a₁ + 4d) = 2a₁ + 8d ( subtract 2a₁ + 8d from both sides )

- a₁ - 2d = 0 → (1)

The sum to n terms of an AP is

S_{n} = \frac{n}{2} [ 2a₁ + (n - 1)d ]

Given S_{7} = 84 , then

\frac{7}{2} (2a₁ + 6d) = 84

3.5(2a₁ + 6d) = 84 ( divide both sides by 3.5 )

2a₁ + 6d = 24 → (2)

Thus we have 2 equations

- a₁ - 2d = 0 → (1)

2a₁ + 6d = 24 → (2)

Multiplying (1) by 3 and adding to (2) will eliminate d

- 3a₁ - 6d = 0 → (3)

Add (2) and (3) term by term to eliminate d

- a₁ = 24 ( multiply both sides by - 1 )

a₁ = - 24

You might be interested in
Question help on this problem! Please
Ostrovityanka [42]

Answer:

Step-by-step explanation:

hi: the second, the third and the last one are true

5 0
2 years ago
Read 2 more answers
What is 442.1 × 11 =​
Marta_Voda [28]

Answer: 4,863.1

Step-by-step explanation:

7 0
3 years ago
With a little care, you can find the median and the quartiles from the histogram. what are these numbers? you can also find the
coldgirl [10]

Complete Question

The histogram from this question is shown on the first uploaded image

Answer:

The first quartile is  1st Q = 19^{th} girl (subject ) = 1 \serving\ of\ fruit\ per\ day

The median is   Median  = 38 ^{th} \ girl (subject) =  2 \serving\ of\ fruit\ per\ day

The third quartile  is 3rd Q =  56^{th} \  girl (subject) = 4 \serving\ of\ fruit\ per\ day  

The  mean is  \= x = 2.62

Step-by-step explanation:

From the question we are told that

   The total  number of girls is n =  74

Generally the median is mathematically represented as

       Median  =  \frac{\frac{n}{2}  +[ \frac{n}{2} + 1]  }{2}

So

          Median  =  \frac{\frac{74}{2}  +[ \frac{74}{2} + 1]  }{2}

=>         Median  =  \frac{37  +38 }{2}

=>         Median  =37.5 \  girl    

From the histogram 37.5 \approx 38^{th} \ girl fall under 2 fruits per day

Generally the first quartile is mathematically represented as

      1st \ Q =  \frac{\frac{n}{4} + [\frac{n}{4} + 1]  }{2}

=>    1st \ Q =  \frac{\frac{74}{4} + [\frac{74}{4} + 1]  }{2}

=>     1st \ Q = 19 \  girl

From the histogram 19^{th}girl fall under 1 fruit per day

 Generally the third quartile is mathematically represented as

     3rd\  Q =  \frac{\frac{n}{2}  + n }{2}

=>    3rd\  Q =  \frac{\frac{74}{2}  + 74 }{2}

=>    3rd\  Q =  55.5

From the histogram 55.5 \approx 56^{th} \ girl fall under 4 fruits per day

Generally from the histogram table the frequency  [number of subjects (girls) ]  and the servings of fruit per day can be represented as

                                                                                                               Total

x(servings per day )        0     1     2     3     4     5    6     7      8    

f (number of subjects )   15    11   15     11    8     5    3     3      3    \sum f  =  74

xf                                       0    11    30   33   32  25   18   21     24    \sum xf =  194

Generally the mean is mathematically represented as

      \= x = \frac{1}{ \sum f}  * [\sum xf]

=>     \= x = \frac{1}{ 74}  *194

=>      \= x = 2.62

4 0
3 years ago
Select all the values of x from this list that make the inequality <br><br><br> FOR POINTS!
denis23 [38]
The answer would be A D E
8 0
3 years ago
A train is traveling at a constant speed and goes a distance of 7 1/2 kilometers in 6 minutes the train will continue at this sp
Alla [95]

Answer:

392939939393939399393939393

Step-by-step explanation:

7 0
3 years ago
Other questions:
  • What are 3 equivalent ratios for 32/24
    6·2 answers
  • It is literal equations please help me
    8·1 answer
  • Brian runs 4 miles in 34 minutes. How many minutes per mile does Brian run?
    8·2 answers
  • When constructing a confidence interval for a population mean, if a population is normally distributed and a small sample is tak
    6·1 answer
  • 1∕2x – 2y + 2z –3z + 3∕4x – y
    13·1 answer
  • Need help with 16-20
    8·1 answer
  • Find each angle measure in the triangle.<br> 3x°<br> 2xº<br> 4xº
    13·2 answers
  • In ΔDEF, the measure of ∠F=90°, DF = 24, FE = 7, and ED = 25. What ratio represents the sine of ∠E?
    15·1 answer
  • A ladder is leaning up against the side of a house. Use two points
    7·1 answer
  • Which statements about the system are true? Select two options.
    12·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!