Why is $Kcdot f(n) + L cdot g(n) leq (K+L) cdot (f(n) + g(n)) $?












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$begingroup$


$Kcdot f(n) + L cdot g(n) leq (K+L) cdot (f(n) + g(n)) $



$n, f(n), g(n), K, L in R^+$



I've seen this inequality a few times in my algorithms course, but I am trying to understand how it works. I would also like to know if it has a name.



An example of someone using it is in the solution to R-3.16










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  • 1




    $begingroup$
    Are $f, g$ functions into non-negative numbers, and $K, L$ non-negative numbers? Then simply expand the parentheses on the right hand side. You get the left hand side, plus something non-negative.
    $endgroup$
    – Mees de Vries
    Jan 29 at 17:25










  • $begingroup$
    You are right, it is the case because of the context. Thank you
    $endgroup$
    – Cedric Martens
    Jan 29 at 17:31
















0












$begingroup$


$Kcdot f(n) + L cdot g(n) leq (K+L) cdot (f(n) + g(n)) $



$n, f(n), g(n), K, L in R^+$



I've seen this inequality a few times in my algorithms course, but I am trying to understand how it works. I would also like to know if it has a name.



An example of someone using it is in the solution to R-3.16










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    Are $f, g$ functions into non-negative numbers, and $K, L$ non-negative numbers? Then simply expand the parentheses on the right hand side. You get the left hand side, plus something non-negative.
    $endgroup$
    – Mees de Vries
    Jan 29 at 17:25










  • $begingroup$
    You are right, it is the case because of the context. Thank you
    $endgroup$
    – Cedric Martens
    Jan 29 at 17:31














0












0








0





$begingroup$


$Kcdot f(n) + L cdot g(n) leq (K+L) cdot (f(n) + g(n)) $



$n, f(n), g(n), K, L in R^+$



I've seen this inequality a few times in my algorithms course, but I am trying to understand how it works. I would also like to know if it has a name.



An example of someone using it is in the solution to R-3.16










share|cite|improve this question











$endgroup$




$Kcdot f(n) + L cdot g(n) leq (K+L) cdot (f(n) + g(n)) $



$n, f(n), g(n), K, L in R^+$



I've seen this inequality a few times in my algorithms course, but I am trying to understand how it works. I would also like to know if it has a name.



An example of someone using it is in the solution to R-3.16







algorithms






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share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 29 at 17:33







Cedric Martens

















asked Jan 29 at 17:24









Cedric MartensCedric Martens

375214




375214








  • 1




    $begingroup$
    Are $f, g$ functions into non-negative numbers, and $K, L$ non-negative numbers? Then simply expand the parentheses on the right hand side. You get the left hand side, plus something non-negative.
    $endgroup$
    – Mees de Vries
    Jan 29 at 17:25










  • $begingroup$
    You are right, it is the case because of the context. Thank you
    $endgroup$
    – Cedric Martens
    Jan 29 at 17:31














  • 1




    $begingroup$
    Are $f, g$ functions into non-negative numbers, and $K, L$ non-negative numbers? Then simply expand the parentheses on the right hand side. You get the left hand side, plus something non-negative.
    $endgroup$
    – Mees de Vries
    Jan 29 at 17:25










  • $begingroup$
    You are right, it is the case because of the context. Thank you
    $endgroup$
    – Cedric Martens
    Jan 29 at 17:31








1




1




$begingroup$
Are $f, g$ functions into non-negative numbers, and $K, L$ non-negative numbers? Then simply expand the parentheses on the right hand side. You get the left hand side, plus something non-negative.
$endgroup$
– Mees de Vries
Jan 29 at 17:25




$begingroup$
Are $f, g$ functions into non-negative numbers, and $K, L$ non-negative numbers? Then simply expand the parentheses on the right hand side. You get the left hand side, plus something non-negative.
$endgroup$
– Mees de Vries
Jan 29 at 17:25












$begingroup$
You are right, it is the case because of the context. Thank you
$endgroup$
– Cedric Martens
Jan 29 at 17:31




$begingroup$
You are right, it is the case because of the context. Thank you
$endgroup$
– Cedric Martens
Jan 29 at 17:31










2 Answers
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1












$begingroup$

Since $K, L, f(n), g(n)$ are all non-negative numbers, expanding the right hand side of the inequality gives the left hand side plus something non-negative.






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$endgroup$





















    0












    $begingroup$

    $$(K+L).(f(n) + g(n)) = K.f(n) + L.g(n) + K.g(n) + L.f(n)$$



    if $K.g(n) geq 0$ and $L.f(n) geq 0$ then they only increase the value of the RHS which makes it greater than or equal to the first two terms: $K.f(n) + L.g(n)$. Hence:
    $$K.f(n) + L.g(n) leq (K+L).(f(n) + g(n)) $$






    share|cite|improve this answer









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      2 Answers
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      2 Answers
      2






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      1












      $begingroup$

      Since $K, L, f(n), g(n)$ are all non-negative numbers, expanding the right hand side of the inequality gives the left hand side plus something non-negative.






      share|cite|improve this answer









      $endgroup$


















        1












        $begingroup$

        Since $K, L, f(n), g(n)$ are all non-negative numbers, expanding the right hand side of the inequality gives the left hand side plus something non-negative.






        share|cite|improve this answer









        $endgroup$
















          1












          1








          1





          $begingroup$

          Since $K, L, f(n), g(n)$ are all non-negative numbers, expanding the right hand side of the inequality gives the left hand side plus something non-negative.






          share|cite|improve this answer









          $endgroup$



          Since $K, L, f(n), g(n)$ are all non-negative numbers, expanding the right hand side of the inequality gives the left hand side plus something non-negative.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 29 at 17:32









          Mees de VriesMees de Vries

          17.6k13060




          17.6k13060























              0












              $begingroup$

              $$(K+L).(f(n) + g(n)) = K.f(n) + L.g(n) + K.g(n) + L.f(n)$$



              if $K.g(n) geq 0$ and $L.f(n) geq 0$ then they only increase the value of the RHS which makes it greater than or equal to the first two terms: $K.f(n) + L.g(n)$. Hence:
              $$K.f(n) + L.g(n) leq (K+L).(f(n) + g(n)) $$






              share|cite|improve this answer









              $endgroup$


















                0












                $begingroup$

                $$(K+L).(f(n) + g(n)) = K.f(n) + L.g(n) + K.g(n) + L.f(n)$$



                if $K.g(n) geq 0$ and $L.f(n) geq 0$ then they only increase the value of the RHS which makes it greater than or equal to the first two terms: $K.f(n) + L.g(n)$. Hence:
                $$K.f(n) + L.g(n) leq (K+L).(f(n) + g(n)) $$






                share|cite|improve this answer









                $endgroup$
















                  0












                  0








                  0





                  $begingroup$

                  $$(K+L).(f(n) + g(n)) = K.f(n) + L.g(n) + K.g(n) + L.f(n)$$



                  if $K.g(n) geq 0$ and $L.f(n) geq 0$ then they only increase the value of the RHS which makes it greater than or equal to the first two terms: $K.f(n) + L.g(n)$. Hence:
                  $$K.f(n) + L.g(n) leq (K+L).(f(n) + g(n)) $$






                  share|cite|improve this answer









                  $endgroup$



                  $$(K+L).(f(n) + g(n)) = K.f(n) + L.g(n) + K.g(n) + L.f(n)$$



                  if $K.g(n) geq 0$ and $L.f(n) geq 0$ then they only increase the value of the RHS which makes it greater than or equal to the first two terms: $K.f(n) + L.g(n)$. Hence:
                  $$K.f(n) + L.g(n) leq (K+L).(f(n) + g(n)) $$







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Jan 29 at 17:33









                  Aloagbaye MomoduAloagbaye Momodu

                  163




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