Z varies jointly as the 4th power of x and the 5th power of y
The 4th power of x means we raise x to the power of 4:
x^4
The 5th power of y means we raise y to the power of 5:
y^5
The phrase varies jointly means we have a constant k such that:
z = kx^4y^5
The 4th power of x means we raise x to the power of 4:
x^4
The 5th power of y means we raise y to the power of 5:
y^5
The phrase varies jointly means we have a constant k such that:
z = kx^4y^5