If y varies directly as x, find a linear function which relates them.
-$$y = 18 \text { when } x = 21$$
A) $f ( x ) = 3 x$
B) $f ( x ) = \frac { 7 } { 6 } x$
C) $f ( x ) = \frac { 6 } { 7 } x$
D) $f ( x ) = x - 3$

Question

Quizplus · Accepted Answer

If y varies directly as x, then y = kx for some constant k. Given y = 18 when x = 21, we find k by solving 18 = k(21), which gives k = 18/21 = 6/7. Thus, the function is f(x) = (6/7)x.

If Y Varies Directly as X, Find a Linear Function y=18 when x=21y = 18 \text { when } x = 21y=18 when x=21

If Y Varies Directly as X, Find a Linear Function $y = 18 \text { when } x = 21$