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+6 votes
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Solve min $x^{2}+y^{2}$

subject to

       $x + y \geq 10,$

   $2x + 3y \geq 20,$

           $x \geq 4,$

           $y \geq 4.$

  1. $32$
  2. $50$
  3. $52$
  4. $100$
  5. None of the above
asked in Calculus by Veteran (42k points) | 252 views

4 Answers

+4 votes
Best answer
Answer -> Option B) 50

 x>=4 and y>=4 , So we can take both x =5 & y = 5

x+y >= 10 => Satisfied , 5+5 = 10

2x + 3y >= 20. Satisfied.

This is infact minimum value.

Other options =>

4,4 => x+y constraint fail

4,5 => x+y fail

6,4 => Still giving 52 as sum which is more than 50 !,  This can not  be answer.

7,3 => 49+9 > 58 > 50.
answered by Veteran (46.7k points)
selected by
+1 vote
I think it's the easiest one,
approach - first we just break to the minimum conditions so every thing can be meet. minimum value such that every thing can satisfy is 5 , 5 which gives = 50,

now all the possiblities are decreasing one number and increasing one. but as u think . as u will decrease one number the value that will decrease will be less then the after effect of increasing the other number.
like 4 and 6 . value that decreases due to decreasing it from 5 is (25-16) = 9

but the increase in the value due to increasing 5 to 6 is (36-25)= 11 , so the best answer will be the mid point i.e 5,5 = 50
answered by Veteran (15.2k points)
0 votes

option c) 52

 

Here , we have constraints x>=4 and y>=4

In order to satisfy the equation x+y >= 10 , we need to have min value of x and y as 4 and 6 .

so , min(x2 + y2) = 16+36 = 52

answered by Boss (5.7k points)

why B is not the ans

because minimum of min(x+ y2)

Here , we have constraints x>=4 and y>=4

In order to satisfy the equation x+y >= 10 , we need to have min value of x and y as 5 and 5.

so , min(x+ y2) = 25+25 = 50

@Arjun ,

why 52 is answer ? It should be 50.

 

0 votes
x+y≥10   

  2x+3y≥20,

  x≥4,

  y≥4.

 we have to choose that value of x & y which satifies all the equations,

as well as give the min ( x^ 2 + y^ 2) which can be possible when X= 5 and Y=5  , min ( x^ 2 + y^ 2) = 5^2 + 5^2 = 50
answered by Loyal (2.7k points)
but (5,5) point does not lie in bounded region of this lpp how we are saying (5,5) will be point of convex region should not the answer be (4,6) which gives 52 as answer


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