Question

the third term of a GP is 9 and the fifth term is 16. find the 4th term and the sum of the first four terms ​

Answer 1

Answer: 4th term: 12

Sum: 525/16

Explanation:

(16*9)^1/(1+1)=

144^1/2=12 ==> 4th term

9/12=3/4 ==> rate of change

9*
`(3/4)^(3-2)`=

9*3/4=27/4 ==> 2nd term

27/4*
`(3/4)^(2-1)`=

27/4 * 3/4 =

27*3/(4*4)=81/16 ==> 1st term

Sum formula: 81/16 + 27/4 + 9 + 12=

81/16 + 108/16 + 144/16 + 192/16=525/16