x∈R*
fie x²=t
t+1/t=8
t²+1=8t
t²-8t+1=0
t1,2= (8+/-√(64-4))/2
t1,2=(8+/-√60)/2=(8+/-2√15)/2=(4+/-√15) , ambele >0, deci au sens
+/-√t1 si +/-√t2
x1,2=+/-√(4-√15)
x3,4=+/-√(4+√15)
ALTCEVA
daca se cerea cumva
calculati x+1/x
atunci
(x+1/x)²=x²+2*x*(1/x)+1/x²=x²+2+1/x²=x²+1/x²+2=8+2=10
si x+1/x=+/-√10
