# Calc 3 Range of a function (set of points)

1. Feb 19, 2014

### xtrubambinoxpr

1. The problem statement, all variables and given/known data

See attached image

2. Relevant equations

they are provided in the image. I see the domain is used

3. The attempt at a solution

I can't figure out how they went from step one to step 2. where does the -81 come from and the 9 multiplied to the function in the middle. I tried to figure it out and all i got was divide everything by 9 then multiplying by 18 across to get 9 in the middle but that wont get me 81 on the eft hand side.

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2. Feb 19, 2014

### gopher_p

What happens to the first batch of inequalities when you multiply everything by -9?

3. Feb 19, 2014

### xtrubambinoxpr

Well I'm pretty retarded lol
But what about the greater than or equal to signs? And why weren't they reversed? Like from elementary you learn to flip them if it's anything with a negative number.

4. Feb 19, 2014

### gopher_p

I doubt that very much if you're taking Calc 3. Inexperienced? Almost definitely. Ill prepared? Possibly. Too stupid? Not very likely.

Look again. The inequalities were flipped, and then the whole line was flipped.

5. Feb 19, 2014

### xtrubambinoxpr

Ahhhhh I see it now! Thanks a lot! This helps a lot this section because I couldn't put the pieces together!