Question

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

Answer 1

`f(x)=18`

Explanation:

`"the statement is "f(x)propx`

`"to convert to an equation multiply by k the constant"`
`"of variation"`

`f(x)=kx`

`"to find k use the given condition"`

`f(x)=90" when "x=30`

`f(x)=kxrArrk=(f(x))/x=90/30=3`

`"equation is " color(red)(bar(ul(|color(white)(2/2)color(black)(f(x)=3x)color(white)(2/2)|)))`

`"when "x=6" then"`

`f(x)=3xx6=18`