(x^(2) + y^(2))^(3) = ax^(2)y ..........its painful, but i think it'll help to expand these brackets.
=> x^6 + 3x^4y^2 + 3x^2y^4 + y^6 = ax^2y
now we go through and differentiate implicitly. we add dy/dx to a function when we differentiate with respect to y, we add dx/dx when we differentiate with respect to x, but dx/dx cancels into 1, so we actually don't write it. also note that we need the product rule when we have x * y in any form. so here goes.
=> 6x^5 + 12x^3y^2 + 6x^4y dy/dx + 6xy^4 + 12x^2y^3 dy/dx + 6y^5 dy/dx = 2axy + ax^2 dy/dx ...........now we group everything with dy/dx on one side so we can factor them out.
=> 6x^4y dy/dx + 12x^2y^3 dy/dx + 6y^5 dy/dx - ax^2 dy/dx = 2axy - 6x^5 - 12x^3y^2 - 6xy^4
=> dy/dx(6x^4y + 12x^2y^3 + 6y^5 - ax^2) = 2axy - 6x^5 - 12x^3y^2 - 6xy^4
=> dy/dx = (2axy - 6x^5 - 12x^3y^2 - 6xy^4)/(6x^4y + 12x^2y^3 + 6y^5 - ax^2)
check if i expanded the cubic correctly