Answer:
[tex]a. \: \: x = 3 \: \: and \: 5[/tex]
Step-by-step explanation:
[tex]a. \: \: \: x^2-8x+ 15 = 0 \\ {x}^{2} - 5x - 3x + 15 = 0 \\ x(x - 5) - 3(x - 5) = 0 \\ (x - 3)(x - 5) = 0 \\ x = 3 \: and \: 5[/tex]
[tex]b. \: \: 2x^2 - 5x - 6 =0 \\ x = \frac{5± \sqrt{73} }{4} [/tex]