Question

If f(x) varies directly with x2 and f(x)=10 what is the value of f(x) when x=3

Answer 1

If f(x) varies directly with
`x^2`

If f(x) varies directly with x then we use equation f(x) = kx

where k is the constant of proportionality

So equation becomes
`f(x) = kx^2`

We use the information and find out k

f(x)= 10

`f(x) = kx^2`

`10= kx^2`

`k = (10)/(x^2)`

now we use the value of k and find the value of f(x) when x=3

`f(x) = (10)/(x^2)*x^2`

f(x) = 10

The value of f(x) = 10 when x= 3