Flag Magical Mathematics[Interesting Approach]> if the first term of a gp a1 a2 a3 …. is ...
question mark

if the first term of a gp a1 a2 a3 …. is unity such that 4a2 + 4a3 is lest, then the common ratio of a g.p is

janani , 7 Years ago
Grade 11
anser 1 Answers
Arun

Last Activity: 7 Years ago

Dear Student
$ a_{2}=ra_{1}$
$ a_{3}=r^{2}a_{1}$
$ y=4a_{2}+5a_{3}=4ra_{1}+5r^{2}a_{1}$

To minimize $ y$, set its derivative equal to $ 0$:

$ 0=4a_{1}+10ra_{1}$

$ \boxed{r=-\frac{2}{5}}$
 
Regards
Arun (AskIITians Forum Expert)
If you find this helpful,approve it 

Provide a better Answer & Earn Cool Goodies

star
LIVE ONLINE CLASSES

Prepraring for the competition made easy just by live online class.

tv

Full Live Access

material

Study Material

removal

Live Doubts Solving

assignment

Daily Class Assignments


Ask a Doubt

Get your questions answered by the expert for free