a. Δ = 49 + 64 = 113 113 = numar prim
√Δ = √113 = numar irational
x₁ =( -7 - √113) / 4 x₂ = ( - 7 + √113) / 4 solutii irationale
b. x² -10x -2 = 0 Δ =100 + 8 = 108 =36·3
√Δ = √36√3 = 6√3 3 = numar prim ; √3 = numar irational
x₁ = ( 10 - 6√3 ) /2 = 5 - 3√3 x₂ = 5 + 3√3 solutii irationale