no 12 caranyaa gimana???

nomor a, pakai subtitusi langsung
[tex] {3x}^{?} - {7x}^{2} + 6x - 15 \\ = 3. {2}^{3} - 7. {2}^{2} + 6.2 - 15 \\ = 24 - 28 + 12 - 15 \\ = - 7[/tex]
nomor b, subtitusi langsung
[tex] \frac{5x + 4}{ \sqrt{ {x}^{2} - x + 4 } } \\ = \frac{5.4 + 4 }{ \sqrt{ {4}^{2} - 4 + 4 } } \\ = \frac{20 + 4}{ \sqrt{16} } \\ = \frac{24}{4} = 6[/tex]
nomor c, pemfaktoran
[tex] \frac{ {x }^{2} - 16}{x - 4} \\ = \frac{(x - 4)(x + 4)}{(x - 4)} \\ = (x + 4) \\ = 4 + 4 = 8[/tex]
nomor d, pemfaktoran
[tex] \frac{ {x}^{2} + x - 6 }{ {x}^{2} - 3x + 2} \\ = \frac{(x - 2)(x + 3)}{(x - 1)(x - 2)} \\ = \frac{x + 3}{x - 1} \\ = \frac{2 + 3}{2 - 1} \\ = \frac{5}{1} = 5[/tex]