olve for x: -4|x + 5| = -16

Question

anonymous · Answer

there are 2 different answers i have no idea what to do

chosenmatt · Answer

what do you think?

calculusfunctions · Answer

First divide both sides by -4 to isolate the absolute value expression.

anonymous · Answer

so -1?

calculusfunctions · Answer

Now if |f(x)| = c where c is a positive constant, then the solution is

f(x) = c  OR  f(x) = -c

calculusfunctions · Answer

No!! If you divide both sides of the given equation by -4, then |x + 5| = 4.  Where do you get -1?? lol

anonymous · Answer

i subtracted 5 from both sides after that and got x =-1

calculusfunctions · Answer

OH yes, one of the solutions -1 but that's not the only solution. What's the complete final answer?

anonymous · Answer

x=9? as the other 
solution

calculusfunctions · Answer

|f(x)| = c where c is a positive constant, f(x) = c OR f(x) = -c

If you understand that, then try again.  Show me your steps!!

calculusfunctions · Answer

f(x) = x + 5, and c = 4. Hence if |x + 5| = 4, then x + 5 = 4 and x + 5 = -4. Thus what are the solutions??

jhannybean · Answer

-4|x + 5| = -16

Isolate `|x+5|`

|x+5| = 4

Understand that `|x+5|` means `x+5` and `-(x+5)`

x + 5 = 4                                                      -x - 5 = 4

      x = 4 - 5                                                 -x  = 4 + 5
                                                
                                                                       x = -(4 + 5)

jhannybean · Answer

Solve for both and you will get 2 values of x.

calculusfunctions · Answer

Don't type out the complete solution @Jhannybean . He needs to make the effort to show his work. How is going to learn?