Question

Help? Will fan and give medal for right answer!!

If f(x) varies directly with x2, and f(x) = 75 when x = 5, find the value of f(4)

Answer 1

Just in case you still need help.
$$
f(x)=kx^2\\
f(5)=k5^2=75\\
k=\cfrac{75}{25}=3\\
f(x)=3x^2\\
f(4)=3(4)^2=3\times16=42
$$

Answer 2

the answer is 42? that's not an option o: @ybarrap

Answer 3

3*16=48 not 42