Question

Daca $x+ \frac{1}{x} =3$ , atunci $x^2+ \frac{1}{x^2}$ este egal cu:

A.7 B.9 C.3 D.6

Doresc o explacatie amanuntita!

Answer 1

x+1/x=3
ridicam la patrat
(x+1/x)²=9
x²+2*x*1/x+1/x²=9
x²+1/x²=9-2
x²+1/x²=7

Answer 2

x+1/x=3
 (x+1/x)²=3²
x²+2*x/x+1/x²=9
x²+1/x²+2=9
x²+1/x²=7

R: A.7.