Question

If f(x) varies directly with x^2, and f(x) = 75 when x = 5, find the value of f(4). A)100 B)50 C)48 D)25

Answer 1

that means f(x)=kx²

so
f(5)=75=5²k
solve for k
75=5²k
75=25k
divide by 25
3=k


f(x)=3x² is da equation

so
f(4)=3(4)²
f(4)=3(16)
f(4)=48

C is answer