Explicație pas cu pas:
28
[tex]2x - y = 3 = > y = 2x - 3 \\ {x}^{2} + 2x - 7 = y \\ {x}^{2} + 2x - 7 = 2x - 3 \\ {x}^{2} - 4 = 0 \\ (x - 2)(x + 2) = 0 \\ x = - 2= > y = - 4 - 3 = - 7\\ x = 2 = > y = 4 - 3 = 1[/tex]
37.
[tex]x + y - 2 = 0 = > y = 2 - x\\{x}^{2} - 2x + y = 0 \\ {x}^{2} - 2x + 2 - x= 0 \\ {x}^{2} - 3x + 2 = 0 \\ (x - 1)(x - 2) = 0 \\ x = 1 = > y = 2 - 1 = 1 \\ x = 2 = > y = 2 - 2 = 0[/tex]
43.
[tex]f(m) = 4 \\ = > {m}^{2} - 2m + 4 = 4 \\ {m}^{2} - 2m = 0 \\ m(m - 2) = 0 \\ m = 0 \\ m = 2[/tex]
68.
[tex] {x}^{2} - Sx + P = 0[/tex]
[tex]S = x1 + x2 = 11[/tex]
[tex] \frac{1}{x1} + \frac{1}{x2} = \frac{11}{30} \\ \frac{x1 + x2}{x1 \times x2} = \frac{11}{30} \\ \frac{11}{x1 \times x2} = \frac{11}{30} \\P = x1 \times x2 = 30[/tex]
[tex] {x}^{2} - 11x + 30 = 0[/tex]
