x=a+b+4 and a∝y2, b∝1/y when
y=2, x=18 and when y=1, x=-3. Find x when y=4

1 thought on “x=a+b+4 and a∝y2, b∝1/y when <br /> y=2, x=18 and when y=1, x=-3. Find x when y=4”

1. Answer:

   Step-by-step Therefore A ∝ 1/B or, A = k ∙ 1/B ………………. (1), where k = constant of variation.

   
   

   Given A = 2 when B = 10.

   
   

   Putting these values in (1), we get,

   
   

   2 = k ∙ 1/10

   
   

   or, k = 20.

   
   

   Therefore, the law of variation is: A = 20 ∙ 1/B……………… (2)

   
   

   When B = 4, then from (2) we get, A = 20 ∙ ¼ = 5.

   
   

   Therefore, A = 5 when B = 4.

   
   

   (ii) Since, x ∝ y²
   

   
   

   Therefore, x = m ∙ y² ……………… (1)

   
   

   where m = constant of variation.

   
   

   Given x = 8 when y = 4.

   
   

   Putting these values in (1), we get,

   
   

   8 = m ∙ 42 = 16m

   
   

   or, m = 8/16

   
   

   or, m = 1/2
   

   
   

   Therefore the law of variation is: x = ½ ∙ y² ………….. (2) When x = 32, then from (2) we get,

   
   

   32 = 1/2 ∙ y²

   
   

   or, y² = 64

   
   

   or, y = ± 8.

   
   

   Hence, y = 8 or, – 8 when x = 32. explanation:

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