So here we need to use the chain rule in order to differentiate the equation. To start you take the function inside the bracket x2+4x and differentiate it to Du/Dx= 2x + 4 this is known as u. do the you differentiate u3 to Dy/Du= 3u2 then multiply Du/Dx by Dy/Du to get Dy/Dx 3u2(2x+4) then substitute u back in to complete the problem 3(x2+4x)(2x+4)