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**robynnn****Member**- Registered: 2007-03-18
- Posts: 1

When x = 2. y = 36

y is directly proportional to x²

Hence y=9x²

Then it goes:

z is inversely propotrional to x

When x = 3. z = 2

b) Show that z=cy to the power n, where c and n are numbers c > 0

(find the values of c and n)

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**JaneFairfax****Member**- Registered: 2007-02-23
- Posts: 6,868

*z* is inversely proportional to *x* means *z* = *B*⁄*x* where *B* is a constant. When *x* = 3. *z* = 2 ⇒ *B* = 6.

∴ *x* = 6⁄*z* ⇒ *x*² = 36⁄*z*² ⇒ *y* = 9*x*² = 324⁄*z*²

∴ *z* = 18*y*[sup]−½[/sup]

*Last edited by JaneFairfax (2007-03-18 11:15:26)*

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