Question

If f(x) varies directly with x2, and f(x) = 40 when x = 2, find the value of f(5).

A.100


B.50


C.250


D.25

Answer 1

C.250

Explanation:

If f(x) varies directly with x^2

f(x) = k * x^2

f(x) = 40 when x=2. Substitute these values in

40 = k(2)^2

40 = k*4

Divide by 4

40/4 = 4k/4

10 =k

f(x) = 10x^2

Now we want to find f(x) when x=5. Substituting

f(5) = 10 *5^2

f(5) = 10 *25

f(5) = 250