How do you find the domain of #f( x ) = \frac { x + 3} { x ^ { 2} + 5x - 4}#?

1 Answer
May 12, 2018

#(-oo,-4)uu(-4,-1)uu(-1,oo)#

Explanation:

The denominator of f(x) cannot be zero as this would make f(x) undefined. Equating the denominator to zero and solving gives the values that x cannot be.

#"solve "x^2+5x+4=0rArr(x+4)(x+1)=0#

#rArrx=-4,x=-1larrcolor(red)"are excluded values"#

#x in(-oo,-4)uu(-4,-1)uu(-1,oo)#
graph{(x+3)/(x^2+5x+4) [-10, 10, -5, 5]}