Rifkee Muhd's answer to xinrann's Secondary 4 A Maths question.
sorry can i know why is there a 1/2 square root y?
Using Chain Rule of Differentiation where derivative of y = sqrt(x) is in the form of dy/dx = 1/2sqrt(x) * 1 (the 1 is obtained by differentiating what's inside the square root which in this case is just x. Apply this rule to the question.