If x= log t and y=t2−1, then y′′ at t=1 is
x=logt and y=t2−1
dydx=dydtdxdt=2t1t=2t2
dtdx=t
d2ydx2=ddt(dydx)dtdx=(4t)t=4t2
d2ydx2|t=1=4