If x – 3 is directly proportional to the square of y and x = 5 when y =2, find x when y = 6.
- 30
-
21
- 16
- 12
The correct answer is: B
Explanation
(x – 3) ∝ y2
X-3 = Ky2
K = X-3 / y2
= 5-2/22
= 2/4
= 1/2
∴X-3 = 1/2y2
X-3 = 1/2 (6)2
X-3 = 1/2 x 36/1
X-3 = 18
X = 21
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