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
tatiyna
3 years ago
11

A geometric progression has a third term of 20 and a sum of infinity which is 3 times the first term. Find the first term ​

Mathematics
1 answer:
Anna007 [38]3 years ago
5 0

Answer: the first term is 45

Step-by-step explanation:

Step 1: The formular for the nth term is ar^n-1 and since we're solving for the third term ar^3-1 = ar² which is equal to 20

So ar²= 20 and we make this equation i

Step 2: the formular for the sum of infinity is Sn = a/(1-r) and according the question the sum of infinity is equals to 3 *A ( A means the first term)

Further simplification gives us

3a= a/(1-r)

We simplify Futher by multiplying both sides by (1-r)

3a.(1-r) = a/(1-r).(1-r)

3a(1-r)=a

= 3a-3ar=a

Make 3ar the subject of the formula

3ar= 2a and lets make this equation (ii)

Step 3: From the first equation since ar²=20, let's make a the subject of the formula by dividing both sides by r²

Ar²/r² = 20/r²

A=20/r²lets make this equation (iii)

Step 4: subtitle a as 20/r² into equation (ii)

Since 3ar=2a

Then 3.(20/r²).r = 2. 20/r²

= (60/r²) .r = 40/r²

60/r = 40/r2

Multiplying both sides by r² gives us

60r = 40

Divide both sides by 20 gives us

= 3r= 2

Divide both sides by 3 gives us

= r = 2/3

Step 5: substitute r for 2/3 in equation i

ar²= 20

a. (2/3)2 = 20

= a.4/9 = 20

= 4a = 180

= a = 180/4

a = 45

You might be interested in
Can somebody help me on this one? Plz
QveST [7]

Answer:

y is at most than -8

Step-by-step explanation:

Step 1) You multiply -2 on both sides to get y by itself.

Than you have your answer. Now graph your answer on the number line.

4 0
3 years ago
Evaluate the expression.
vodka [1.7K]

Answer:

-1/3

Step-by-step explanation:

Evaluate the power, -3/9

Simplify the fraction by divided each number by 3, -1/3

Final answer, -1/3

8 0
3 years ago
Read 2 more answers
Find the Quotient.<br>4,298 ÷ 4​
posledela

Answer:

1074.5 or 1074 1/2

Step-by-step explanation:

5 0
3 years ago
Read 2 more answers
Verify cotx/secx=1/sinx-sinx
weeeeeb [17]
Cot=cos\sin
sec=1\cos
cosx\sinx÷1\cosx=
cos^2x\sinx=1-sin^2x\sinx=
1\sinx-sin^2x\sinx= 1/sinx-sinx
3 0
3 years ago
4 to the power of 55
LenaWriter [7]

\\ \sf\longmapsto 4^{55}

\\ \sf\longmapsto (4^5)^{11}

\\ \sf\longmapsto 1024^{11}

\\ \sf\longmapsto 1024^31024^41024^3

\\ \sf\longmapsto 1,073,741,824\times 1,073,741,824\times 1,099,511,627,776

\\ \sf\longmapsto 1.29807421E+33

6 0
2 years ago
Other questions:
  • Freddy is two years old than her brother. Twelve years ago, she was twice as old as he was. How old were they? Equation
    9·1 answer
  • Find the odds of an answer if the probability of the event is given to be 3/8
    14·1 answer
  • Find the inverse of each function y=3^x/4
    13·1 answer
  • If two sides of a rectangle are 5 units and 9 units, what is the perimeter?
    10·1 answer
  • PLEASE HELP...When you have a problem like the one listed below... What do you do with your exponents? ​
    11·2 answers
  • Can sum on help me plzz
    13·1 answer
  • X - 4y = 1 and 3x + 2y = -11. What is the solution to the system of equations?
    7·1 answer
  • En un colegio hay 315 alumnos de los cuales 1/3 son mujeres y el resto hombres. 2/7 de los hombres juegan al fútbol y el resto a
    11·1 answer
  • Find the product binomial expression of;<br><br>(x-5) (8-5)​
    7·1 answer
  • Earlier in this course, you explored Euclidean geometry, which is the study of flat space. This approach follows the teachings o
    15·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!