How do you find the domain of the function $f (x) = \frac{2 x + 3}{x^{2} + 9 x + 20}$ $f(x)= (2x+3)/(x^2+9x+20)$ ?

Question

2286 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-04-16T12:21:36

Any value that makes the denominator $= 0$ $=0$ is forbidden

So we need to know when $x^{2} + 9 x + 20 = 0$ $x^2+9x+20=0$

If we factorise we get:
$(x + 4) (x + 5) = 0 \to x = - 4 or x = - 5$ $(x+4)(x+5)=0->x=-4orx=-5$

So these are not allowed. Any other $x$ $x$ -value is.

Answer : $x \neq - 4 and x \neq - 5$ $x!=-4andx!=-5$

How do you find the domain of the function f(x)=2x+3x2+9x+20f(x)= (2x+3)/(x^2+9x+20)?