pr la 1) pose a =Vx
calculons lim ( x²-Vx)²/(x-1)
=lim (x^4-2x²Vx+x)/(x-1)
= lim (a^8-2a^5+a²)/(a-1)(a+1)
=lim a² ( a-1 )² (a²+a+1)² / (a-1)(a+1)
= lim a² (a-1) (a²+a+1)² / (a+1)
en remplacant a par 1
lim 1*0*9/2 = 0
donc lim(x--->1+)( x²-Vx)/V(x-1)=V(lim ( x²-Vx)²/(x-1))=0