233k views
5 votes
If f(x) = -x/4x-1 and g(x) = 2/x-9, algebraically determine when f(x)>g(x)

If f(x) = -x/4x-1 and g(x) = 2/x-9, algebraically determine when f(x)>g(x)-example-1
User Cao
by
4.4k points

1 Answer

3 votes

\: -1<p></p><p><strong>1) </strong> In this question, to determine when f(x) > g(x) we need to plug into this inequality the given values:</p>[tex]\begin{gathered} f(x)>g(x) \\ (-x)/(4x-1)>(2)/(x-9) \\ Take\: the\: LCM\: for\: the\: denominators \\ (-x(x-9))/((4x-1)(x-9))>(2(4x-1))/((4x-1)(x-9)) \\ (-x^2+x+2)/((4x-1)(x-9))>0 \\ Factor\: the\: numerator \\ (-\mleft(x+1\mright)\mleft(x-2\mright))/((4x-1)(x-9))>0 \\ (\left(x+1\right)\left(x-2\right))/(\left(x-9\right)\left(4x-1\right))<0 \end{gathered}

2) Let's identify the valid intervals for this inequality:


\begin{gathered} x+1<0,x<-1 \\ x-2<0,x<2 \\ x-9<0,x<9 \\ 4x-1<0,x<(1)/(4) \\ \\ \end{gathered}

So the answer is:

[tex]\begin{gathered} \: -1
If f(x) = -x/4x-1 and g(x) = 2/x-9, algebraically determine when f(x)>g(x)-example-1
User Naptoon
by
4.7k points