Question

The function varies directly with x and when x = 30.
f(x)
f(x) = 90
What is when x = 6?
f(x)

Answer 1

The function f(x) varies directly with x and f(x) = 90 when x = 30.

f(x)=3x

What is f(x) when x = 6?

f(6)= 3*6 =18

18

Answer 2

Answer:

$f(6)=18$

In words, the image assigned to $x=6$ is 18.

Step-by-step explanation:

Givens

• The function varies directly.
• When $x=30$, $f(x)=90$.

When a function varies directly, it means that function is linear, and it has a direct proportion between variables, so can be modeled by $f(x)=mx$, where $m$ is the constant ratio of change.

So, in this case, the ratio of change is

$m=\frac{\Delta y}{\Delta x}=\frac{90}{30}=3$

That means the linear function that represents this situation is

$f(x)=3x$

So, if $x=6$, then

$f(x)=3x\\f(6)=3(6)=18$

Therefore, $f(6)=18$