[(2/3)^2+1]^2÷13-(2 rad.2 +1)(2rad2-1) [(4/9)+1]^2÷13-..... formula de calcul prescurtat: (a+b)(a-b)=a^2-b^2=> [(4/9)+1]^2÷13-(8-1) in prima paranteza se aduce la acealsi numitor=> (4+9/9)^2÷13-7 (13/9)^2-6 (169/81)-6 se aduce la acelasi numitor 169-486/81 −317/81
