# absolute values are SCArY!!!

• Aug 26th 2009, 05:46 PM
jazzyredsox5
absolute values are SCArY!!!
i understand that an absolute value is the distance on a number line from zero, and that abs(y)=8 would be 8, -8, but when it gets to like abs(c/4)=9, i know you have to make two equations, c/4=9 and c/4=-9, because my sheet says so, but why? i don't understand why the 9 is affected when it is not in the absolute value bars.......(Surprised)
• Aug 26th 2009, 05:59 PM
pickslides
By definition $|a|\leq b \Rightarrow -b \leq a \leq b$

Why?

Look at the function $y = |x|$
• Aug 26th 2009, 06:12 PM
jazzyredsox5
[quote=pickslides;355065]By definition $|a|\leq b \Rightarrow -b \leq a \leq b$

i was never taught absolute value by that equation before... so if abs(w-8)=7, then would i set up the equation to be w-8=16 and w-8=-16 and then solve?
• Aug 26th 2009, 06:26 PM
pickslides
Quote:

Originally Posted by jazzyredsox5
so if abs(w-8)=7, then would i set up the equation to be w-8=16 and w-8=-16 and then solve?

So what are you asking? I am confused how 7 can be equal to 16?

I'm guessing you are saying $|w-8|\leq 7 \Rightarrow -7 \leq w-8 \leq 7$

Therefore solve both

$-7 \leq w-8$

$1 \leq w$

$w \geq 1$

and

$w-8 \leq 7$

$w \leq 15$