1. ## Trig Problem

Hey can you show me how to find the x- Intercepts for cos(y+Pi) = x^2 -x - 7

I tried a bunch of different things but I can't figure it out: the answer is supposed to be 3 (I like the faces )

2. Originally Posted by Mudd_101
Hey can you show me how to find the x- Intercepts for cos(y+Pi) = x^2 -x - 7

I tried a bunch of different things but I can't figure it out: the answer is supposed to be 3 (I like the faces )
as always, x-intercepts occur where y = 0. so plug in y = 0, we have

$\displaystyle \cos \pi = x^2 - x - 7$

$\displaystyle \Rightarrow -1 = x^2 - x - 7$

$\displaystyle \Rightarrow x^2 - x - 6 = 0$

3. Originally Posted by Mudd_101
Hey can you show me how to find the x- Intercepts for cos(y+Pi) = x^2 -x - 7

I tried a bunch of different things but I can't figure it out: the answer is supposed to be 3 (I like the faces )
It intercepts the x axis when y is zero!

$\displaystyle \cos(0+\pi) = x^2 -x - 7$

$\displaystyle \cos(\pi) = x^2 -x - 7$

$\displaystyle -1 = x^2 -x - 7$

$\displaystyle x^2 -x - 6 = 0$

$\displaystyle (x-3)(x+2) = 0$

$\displaystyle x = 3 \text{ or } x = -2$

4. OO thanks (silly me put x as 0)