Question

the sum of 3 numbers in a.p.is 15 and the product of the first and the last is 21 find the number ​

Answer 1

Answer:

3. 5. 7.....

ans

thanks..........

Answer 2

Explanation:

Solution:- 3 , 5 , 7 .

Given :- In A.P. ,

Sum of three numbers = 15

product of first and last = 21

To Find out :-

What're the numbers .

Explanation :-

a + a+d + a+2d = 15

3a + 3d = 15

a + d = 5 --------(1)

Now , a(a + 2d) = 21

a + 2d = 21/a -------(2)

From equation (1) & (2)

a + 5 + 21/a = 15

a² + 5a + 21 = 15a

a² - 10a + 21 = 0

a² - 7a - 3a + 21 = 0

(a - 7) (a - 3) = 0

a = 7 , 3

Now

when a = 7 , then d = -2 no. are 7 , 5 , 3

when a = 3 , then d = 2 no. are 3 , 5 , 7

At the end ,

The numbers are 3 , 5 & 7 .