[tex]f:\mathbb{R}\rightarrow\mathbb{R} \: \: \: ,f(x)=-3mx+5m-7 \: \: \: ,m\:\in\:\mathbb{{R}^{*}}[/tex]
[tex]M(m;{m}^{2}-3m-7)\:\in\:G_{f} < = > f(m) = {m}^{2} - 3m - 7[/tex]
[tex]f(m) = - 3m \times m + 5m - 7[/tex]
[tex]f(m) = - 3 {m}^{2} + 5m - 7[/tex]
[tex] - 3 {m}^{2} + 5m - 7 = {m}^{2} - 3m - 7[/tex]
[tex] - 3 {m}^{2} - {m}^{2} + 5m + 3m - 7 + 7 = 0[/tex]
[tex] - 4 {m}^{2} + 8m = 0 \: | \div ( - 4)[/tex]
[tex] {m}^{2} - 2m = 0[/tex]
[tex]m(m - 2) = 0[/tex]
[tex]m = 0 \: nu \: convine[/tex]
[tex]m - 2= 0 => m = 2 \: \in \: \mathbb{{R}^{*}}[/tex]
