# Math Help - Troubled on some kind of limit problem...

1. ## Troubled on some kind of limit problem...

I can't seem to figure out for what value of the constant c is the function f continuous on negative infinity to positive infinity

2. Originally Posted by frozenflames

I can't seem to figure out for what value of the constant c is the function f continuous on negative infinity to positive infinity
For it to be continous it needs to be continous at b=9

This mean that

$\lim_{b \to 9^-}f(b)=f(9)=\lim_{b \to 9^+}f(b)$

so we need to sove $9c+5=81c-5 \iff 10=72c \iff c=\frac{5}{32}$

3. Originally Posted by TheEmptySet
For it to be continous it needs to be continous at b=9

This mean that

$\lim_{b \to 9^-}f(b)=f(9)=\lim_{b \to 9^+}f(b)$

so we need to sove $9c+5=81c-5 \iff 10=72c \iff c=\frac{32}{5}$
I think you did the final part of the math wrong. It should be 10/72 not the other way around right?

4. Originally Posted by frozenflames
I think you did the final part of the math wrong. It should be 10/72 not the other way around right?
You shouldn't need re-assurance on how to solve $10 = 72c$. The typo is obvious.