Assume that y varies inversely as x. If y = - 8 when x = - 9, find y when x = 4.

y = 18

y = 72

y = 4.5

Y α 1/x

y = k/x Where k is the constant of proportionality.

xy = k Cross Multiplying.

k = xy

Recall y = - 8 when x = - 9

k = - 9 * - 8 = 72

Finding y when x = 4.

k = xy

72 = 4y Divide both sides by 4.

y = 72/4 = 18.

y = 18.