72 
MEMORIAS CIENTIFICAS I LITERARIAS 
dx = — 2z dz, y = — / (a — z 2 ) 2 z 2 d z 
2 '32 ,3 
= ~ a (a — x) 2 - (a — x)T . 
t) 0 
(Roberts, 10) 
2. y=/ x Va-|-xdx, Seaa-|-x = t 2 dx = 2tdt 
y = 2/ (t* 2 — a) 2 t 2 d t = 2 
2 at 5 a 2 t 3 \ 
5 ^ 3 / 
, JL ( (a-fx) 2 2a, , , , a 2 | 
=2 (a + x) 2 | — ^ — ( a + x ) + j 
(Todhunter, 18) 
3. y = f — ^ X . Hacemos l-J-x 2 = z* 
■ J Vl+X* 
Diferenciamos: 
2xdx = 2zdz 
Componemos: 
dx + dz _ d (x-f-z) dx 
z+x ~~ z+x ~ z 
