y varies partly as the square of x and partly as the inverse of the...

JAMB 1983

y varies partly as the square of x and partly as the inverse of the square root of x.Write down the expression for y if y = 2 when x = 1 and y = 6 when x = 4

A. y = \(\frac{10x^2}{31} + \frac{52}{31\sqrt{x}}\)
B. y = x² + \(\frac{1}{\sqrt{x}}\)
C. y = x² + \(\frac{1}{x}\)
D. y = \(\frac{x^2}{31} + \frac{1}{31\sqrt{x}}\)

WAEC and NECO CBT Software for Computers and Laptops - Candidates, Schools, Centres, Resellers - 100% Offline -Download Now

Your School's Whatsapp Group - Join Us now

Correct Answer: Option A

Explanation

y = kx² + \(\frac{c}{\sqrt{x}}\)

y = 2when x = 1

2 = k + \(\frac{c}{1}\)

k + c = 2

y = 6 when x = 4

6 = 16k + \(\frac{c}{2}\)

12 = 32k + c

k + c = 2

32k + c = 12

= 31k + 10

k = \(\frac{10}{31}\)

c = 2 - \(\frac{10}{31}\)

= \(\frac{62 - 10}{31}\)

= \(\frac{52}{31}\)

y = \(\frac{10x^2}{31} + \frac{52}{31\sqrt{x}}\)

Previous Next

Go back to Maths classroom

Report an Error Ask A Question Download App