+0  
 
0
845
1
avatar

 please help with this problem!!!!!
The variable z varies jointly with x and y and inversely with the square of t. Also, z=5 when x=2, y=-3, and t=1/2. Write a function such that f(y)=t when x=-12/(5z)^2 and z=2/5. 

f(y)=________ ????????

 Aug 29, 2016
 #1
avatar+33653 
+1

1.  z(x,y,t) = k*x*y/t   where k is a constant

 

We know that 5 = k*2*(-3)/(1/2) or 5 = -12k  so k = -5/12  

 

Hence z(x,y,t) = -5xy/(12t)

 

2. When x = -12/(5z)^2  we have z = -5*(-12)/(5z)^2*y/(12t)  or  z = y/(5z^2*t)  or t = y/(5z^3)  

     Since z = 2/5  then t = y/(5*2^3/5^3)   or  t =  25y/8

 

3.  Since f(y) = t we must have f(y) = 25y/8

 

(check the algebra - I did this quickly!)

.

 Aug 29, 2016

2 Online Users