quadratic

minimum value of (a+b+c+d)(1/a+1/b+1/c+1/d) is

7 Answers

1
greatvishal swami ·

1??

1
voldy ·

no . try the Am Hm inequality , we get 16 , as the min value.

or , the rule.
I dunno . waht it's called . plugging in a=b=c=d=1 . we get the min as 16 .

It's some theorem . I dunno . the min occurs at ±1 .

Better not confuse you . ask Nishant or Abhishek. they'll know better.

1
greatvishal swami ·

i m nt with dat +- like thng as its value is 16 for all 2n like numbers

bt yup i made a mistake ans is 16

1357
Manish Shankar ·

Try AM≥HM here

(a+b+c+d)/4≥4/(1/a +1/b +1/c +1/d)

(a+b+c+d)(1/a +1/b +1/c +1/d)≥16

so minimum value is 16

1
dimensions (dimentime) ·

or, by cauchy schwarz inequility,

(a/a+b/b+c/c+d/d)2≤(a+b+c+d)(1/a+1/b+1/c+1/d)

=> (a+b+c+d)(1/a+1/b+1/c+1/d) ≥ 16

so the minimum value is 16

1
rahul1993 Duggal ·

33
Abhishek Priyam ·

Since the question is symmetric in a,b,c,d so min occurs at a=b=c=d...

As why you will give preference to any one of them (others will get angry..)

this method is quite helpful in objectives but not so dependenable....

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