Question

Find 3 number in a.p who's sum is 15 and product of first $ last terms is 21.Find the numbers

Answer 1

Answer:

3,5 and 7

Step-by-step explanation:

let the numbers be a-d, a and a+d

the sum of three numbers be 15

$(a - d) + a + (a + d) = 15 \\ 3a = 15 \\ a = 5$

product of first and last term be 21

$( a- d)( a+ d) = 21 \\ {a}^{2} - {d}^{2} = 21 \\ {5}^{2} - {d}^{2} = 21 \\ - {d}^{2} = 21 - 25 \\ - {d}^{2} = - 4 \\ {d}^{2} = 4$

$d = \sqrt{4} \\ d= 2$

Then the terms be a-d,a and a+d

5-2,5,5+2

3,5,7.