Question

Sa-mi spuneti cum ati facut. :)

Answer 1

folosesti formula de calcul prescurtat
 (a+1/a)²=a²+2a*1/a+(1/a)²=a²+(1/a)²+2=7+2=9

Answer 2

$a^2+\dfrac{1}{a^2}=27\Rightarrow a^2+2\cdot a\cdot\dfrac{1}{a}+\dfrac{1}{a^2}=7+2$

$(a+\dfrac1a)^2=9\Rightarrow a+\dfrac1a=\pm3$