Given that y varies inversely as the square of x. If x = 3 when
MATHEMATICS
WAEC 2018
Given that y varies inversely as the square of x. If x = 3 when y = 100, find the equation connecting x and y.
- A. \(yx^2 = 300\)
- B. \(yx^2 = 900\)
- C. y = \(\frac{100x}{9}\)
- D. \(y = 900x^2\)
Correct Answer: B. \(yx^2 = 900\)
Explanation
Y \(\alpha \frac{1}{x^2} \rightarrow y = \frac{k}{x^2}\)
If x = 3 and y = 100,
then, \(\frac{100}{1} = \frac{k}{3^2}\)
\(\frac{100}{1} = \frac{k}{9}\)
k = 100 x 9 = 900
Substitute 900 for k in
y = \(\frac{k}{x^2}\); y = \(\frac{900}{x^2}\)
= \(yx^2 = 900\)
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