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I still need help on both 6.28 and 6.30 II-A

 
 
YangBober的头像
I still need help on both 6.28 and 6.30 II-A
YangBober - 2020年07月19日 Sunday 21:23
 

Thank you

 
LensmireJohn的头像
Re: I still need help on both 6.28 and 6.30 II-A
LensmireJohn - 2020年07月20日 Monday 10:38
 

I know this is a little late, but here are some hints.

For 6.28: Consider the discriminant. First try completing the square for the terms that only have the variable $a$. Can you factor what is left?

For 6.30: The domain is all real numbers (no things to worry about here with absolute values). For the range, we know that absolute values are always $\geq 0$. Can this help? For finding the zeros (or in general for the above) it might help to consider at least a few cases to see what happens with the function.