If y varies directly as x, find a linear function which relates them.
-$y = 18$ 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

Since y varies directly as x, the relationship is $y = kx$. Given $y = 18$ when $x = 21$, solve for k: $18 = k \times 21$, so $k = \frac{6}{7}$. Thus, the function is $f(x) = \frac{6}{7}x$.

If Y Varies Directly as X, Find a Linear Function y=18y = 18y=18

If Y Varies Directly as X, Find a Linear Function $y = 18$