Can u plz help me with this precalc problem?

Question

y varies jointly with the cube of x and the square of z and inversely with the square of the sum of x and z if y = 72 when x= 2 and z=3 , then find the value of y when x= -1 and z=5.....thx...... I am very lost plz explain all work and answers in detail thx

Note jointly means multiplied inversely in devide

Answer 1

Ok..its simple. Now lets tale the first case. x=2 and z=3. y varies jointly with the cube of x and the square of z....cube of x is 2^3 which is 8 and square of z is 3^2 ehich is 9. So 8*9=72

Similarly do the second case.

y = {x^3=-1^3=-1 Multiplied by z=5^2=25}

therefore y=25*-1 which is nothing but -25.

The other information is redundant.