# increasing decreasing

• August 6th 2007, 01:41 PM
aikenfan
increasing decreasing
Find the intervals on which y = (x +4)^2 - 7 is increasing or decreasing

thank you!
• August 6th 2007, 02:16 PM
aikenfan
where did the 9 come from?
• August 6th 2007, 02:27 PM
topsquark
Quote:

Originally Posted by aikenfan
Find the intervals on which y = (x +4)^2 - 7 is increasing or decreasing

thank you!

Quote:

Originally Posted by aikenfan
where did the 9 come from?

$y = (x + 4)^2 - 7 = (x^2 + 8x + 16) - 7 = x^2 + 8x + 9$

-Dan
• August 6th 2007, 02:29 PM
topsquark
Quote:

Originally Posted by aikenfan
Find the intervals on which y = (x +4)^2 - 7 is increasing or decreasing

$y = a(x - h)^2 + k$
So the vertex of $y = (x + 4)^2 - 7$ is at (-4, -7) and a = 1. Thus it opens upward. So it must be decreasing on $( - \infty, -4)$ and increasing on $(-4, \infty)$.