Question

if x-3 is a factor x2-ax-15,then the value of a is​

Answer 1

Answer:

I hope this is helpful to you

Answer 2

Here is your solution.

$let \: f(x) = \: {x}^{2} - ax - 15 \\ if \: (x - 3) \: is \: a \: factor \: of \: f(x) \: then \\ f(3)= 0 \: \: by \: factor \: theorem \\ {3}^{2} - (a \times 3) - 15 = 0 \\ 9 - 3a - 15 = 0 \\ - 3a - 6 = 0 \\ - 3(a + 2) = 0 \\ a + 2 = 0 \\ a = 0 - 2 \\ a = - 2$

Final answer : a= -2