MATHEMATICS

JAMB 2008 - Question 15

Mathematics 2008 JAMB Past Questions - Question 15: if x-3 is directly proportional to the square of y and x=5 when y=2 find x when y=6.

if x-3 is directly proportional to the square of y and x=5 when y=2 find x when y=6.
A:
B:
C:
D:
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Correct Answer

B

Explanation

x – 3 = ky², i.e. x – 3 = 18 x = 21 If x - 3 is directly proportional to the square of y, we can express this relationship as:x - 3 = k * y^2where k is the constant of proportionality.Given that x = 5 when y = 2, we can substitute these values into the equation to solve for k:5 - 3 = k * 2^22 = 4kk = 2/4k = 1/2Now that we have the value of k, we can use it to find x when y = 6:x - 3 = (1/2) * 6^2x - 3 = (1/2) * 36x - 3 = 18x = 18 + 3x = 21Therefore, when y = 6, x = 21.