z is jointly proportional to the square of x and the cube of y
The square of x means we raise x to the power of 2:
x^2
The cube of y means we raise y to the power of 3:
y^3
The phrase jointly proportional means we have a constant k such that:
z = kx^2y^3
The square of x means we raise x to the power of 2:
x^2
The cube of y means we raise y to the power of 3:
y^3
The phrase jointly proportional means we have a constant k such that:
z = kx^2y^3