Question

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

Answer 1

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.