If y=1(a-z), then dzdy=
a-z2
-z-a2
z+a2
-z+a2
Explanation for the correct option :
Step 1: Express z in terms of y.
y=1(a-z)⇒ay-yz=1⇒z=a-1y ........ 1
Step 2: Find dzdy
By differentiating 1 w.r.t y, we get
dzdy=ddya-1y=0+1y2=11a-z2=a-z2
Hence, option A is correct.