a) (x+1/x)^2=5^2; x^2+2x*1/x+1/x^2=25; x^2+2+1/x^2=25; X^2+1/x^2=25-2=23
b) (x+1/x)^3=5^3; (x^2+2x*1/x+1/x^2)(x+1/x)=125; x^3+x^2/x+2x+2/x+x/x^2+1/x^3=125;
x^3+x+2x+2/x+1/x+1/x^3=125; x^3+3x+3/x+1/x^3=125;
x^3+1/x^3+3(x+1/x)=125; x^3+1/x^3+3*5=125;
x^3+1/x^3=125-15=110;
c), d)... in acelasi mod
