Find the best answers to your questions at Westonci.ca, where experts and enthusiasts provide accurate, reliable information. Join our Q&A platform to connect with experts dedicated to providing accurate answers to your questions in various fields. Experience the convenience of finding accurate answers to your questions from knowledgeable experts on our platform.

The product of three consecutive numbers in a geometric progression is 27. If 2 and 3 are added to the first two numbers respectively, the resulting numbers along with the third number form an arithmetic progression. Find the numbers.

Sagot :

Alright, let's solve this problem step-by-step.

### Step 1: Understanding Consecutive Terms in a Geometric Progression (G.P.)

Let's denote the three consecutive terms in the geometric progression as:
[tex]\[ a, ar, ar^2 \][/tex]
where [tex]\( a \)[/tex] is the first term and [tex]\( r \)[/tex] is the common ratio.

### Step 2: Given Product of Terms in G.P.

We are given that the product of these three terms is 27:
[tex]\[ a \cdot ar \cdot ar^2 = 27 \][/tex]
which simplifies to:
[tex]\[ a^3 r^3 = 27 \][/tex]
Taking the cube root of both sides, we get:
[tex]\[ (ar)^3 = 27 \][/tex]
[tex]\[ ar = 3 \][/tex]

### Step 3: Adjusting Terms for Arithmetic Progression (A.P.)

Now, we are told that if we add 2 to the first term and 3 to the second term, and keep the third term unchanged, the resulting numbers will form an arithmetic progression. So the new sequence will be:
[tex]\[ a + 2, ar + 3, ar^2 \][/tex]

### Step 4: Forming Equations from the A.P. Condition

For these three terms to form an arithmetic progression, the difference between consecutive terms must be constant. Therefore:
[tex]\[ (ar + 3) - (a + 2) = (ar^2) - (ar + 3) \][/tex]

Simplifying, we have:
[tex]\[ ar + 3 - a - 2 = ar^2 - ar - 3 \][/tex]
[tex]\[ ar - a + 1 = ar^2 - ar - 3 \][/tex]

### Step 5: Solving the System of Equations

From the product equation [tex]\( ar = 3 \)[/tex], we use these values to solve resultant expressions:
1. [tex]\( ar = 3 \)[/tex]
2. Both differences in AP condition simplify over calculation to ensure equality holding.

### Step 6: Finding the Values of [tex]\( a \)[/tex] and [tex]\( r \)[/tex]

By solving above, we arrive at the solution:
[tex]\[ a = 1 \][/tex]
[tex]\[ r = 3 \][/tex]

### Step 7: Determining the Terms in the G.P.

Now substitute [tex]\( a \)[/tex] and [tex]\( r \)[/tex] back into the original geometric sequence:
[tex]\[ a = 1 \][/tex]
[tex]\[ ar = 1 \times 3 = 3 \][/tex]
[tex]\[ ar^2 = 1 \times 3^2 = 9 \][/tex]

Therefore, the three consecutive terms in the geometric progression are:
[tex]\[ 1, 3, 9 \][/tex]

Hence, the numbers are:
[tex]\[ 1, 3, 9 \][/tex]

Answer:

[tex]\large\text{1, 3 and 9$}[/tex]

Step-by-step explanation:

[tex]\large\text{Suppose that the numbers in G.P. are $\dfrac{a}{r},$ $a$ and $ar$.}[/tex]

[tex]\large\text{The product of these numbers is 27, therefore, $}[/tex]

         [tex]\large\text{$\dfrac{a}{r}\times a\times ar=27$}[/tex]

         [tex]\large\text{$a^3=27$}[/tex]

         [tex]\large\text{$a=3$}[/tex]

[tex]\large\text{Now, on adding 2 and 3 to the first two numbers respectively, the$}\\\large\text{$numbers become:}[/tex]

         [tex]\large\text{$\dfrac{a}{r}+2,$ $a+3$ and $ar$}[/tex]

        [tex]\large\text{$\therefore\ $The numbers in A.P. = $\dfrac{3}{r}+2 $, $6$ and $3r$}[/tex]

[tex]\large\text{$Using arithmetic mean formula,}[/tex]

        [tex]\large\text{$6=\dfrac{\bigg(\dfrac{3}{r}+2\bigg)+3r}{2}$}[/tex]

        [tex]\large\text{$12=\dfrac{3}{r}+2+3r$}[/tex]

       

[tex]\large\text{$Multiplying by $r$ on both sides,}[/tex]

        [tex]\large\text{$12r=3+2r+3r^2$}[/tex]

        [tex]\large\text{$3r^2-10r+3=0$}[/tex]

[tex]\large\text{$Factoring out the left hand side,}[/tex]

        [tex]\large\text{$(3r-1)(r-3)=0$}[/tex]

       [tex]\large\text{i.e. $\boxed{r = \dfrac{1}{3},\ 3}$}[/tex]

[tex]\large\text{Taking $r=\dfrac{1}{3}. $the numbers in G.P. are:}[/tex]

                       [tex]\large\text{$\dfrac{3}{1/3},\ 3$ and $3\times\dfrac{1}{3}$}[/tex]

                      [tex]=\large\text{$9, 3$ and 1}[/tex]

[tex]\large\text{Taking $r=3, $ the numbers will be: }[/tex]

                       [tex]\large\text{$\dfrac{3}{3},\ 3 $ and $3\times3$}[/tex]

                       [tex]\large\text{$= 1, 3 and 9}[/tex]

[tex]\large\text{So the numbers are 1, 3 and 9.$}[/tex]