Check your original question
if y = x/ ( a^2 - x^2) ^(1/2) - arcsin (x-a)
then you are right
however if y = x/ ( a^2 - x^2) ^(1/2) - arcsin (x/a)
dy/dx = x^2 / ( a^2- x^2) ^(3/2)
See attachment
how do you differentiate
y = x/ ( a^2 - x^2) ^(1/2) - arcsin (x-a)
i tried to differentiate and i got
y' = a^2 / ( a^2- x^2) ^(3/2) - 1/ ( (1-(x-a)^2)^(1/2)
when the answer should be x^2 / ( a^2- x^2) ^(3/2)
may i know how i can continue from where i am stuck at?
thanks