Question

FACT: d/dx((1-x)/1+x))= (-2)/((1+x)^2).
Then the integral of (-2/((1+x)^2)))dx = ((1-x)/(1+x)) + c

EVALUATE : the integral of ((-2/((1+x)^2)) dx by letting u=1+x and du=dx
Do you get the same answer as above? EXPLAIN.