I really need help with this:
write a general formula to describe the variation:
*A varies directly with x^2 ; A=18(pi) when x=3
*F varies inversely with D^2; F=36 when d=6
*M varies directly with the square of D and inversely with the square root of X; M=24 when D=3 and X=16

Question

I really need help with this: 
write a general formula to describe the variation:
*A varies directly with x^2 ; A=18(pi) when x=3
*F varies inversely with D^2; F=36 when d=6
*M varies directly with the square of D and inversely with the square root of X; M=24 when D=3 and X=16

dumbcow · Answer

A = kx^2  --> 18pi = 9k -> k = 2pi
A = 2pi x^2

F = k/d^2  --> 36=k/36 -> k = 36^2 =1296
F = 1296/d^2

M = kd^2/sqrt(x)  --> 24 = 9k/4 -> k = 96/9 = 32/3
M = 32d^2/3sqrt(x)