Simple Maths Algebra (1 Viewer)

[skillstriker]

Expand and simplify square root of {(a-5)(a+5)+25}. The answer says 'a' but why isn't the answer the absolute value of a?

 

[RealiseNothing]

Expand and simplify square root of {(a-5)(a+5)+25}. The answer says 'a' but why isn't the answer the absolute value of a?

 

[skillstriker]

If you sub in a negative number e.g. -2 you get the opposite i.e. 2...so it cant be a. also doesn't the square root of a^2 = |a|?

 

[RealiseNothing]

If you sub in a negative number e.g. -2 you get the opposite i.e. 2...so it cant be a. also doesn't the square root of a^2 = |a|?

Yer it is, I don't know why the answers just say a for.

 

[such_such]

yeah, it should be as you said, |a|

http://www.wolframalpha.com/input/?i=sqrt{(a-5)(a+5)+25}

The graph is absolute and if the answer is from a textbook, you're free to doubt their answers.

 

[Leffife]

√((a-5)(a+5)+25)

= √((a² + 5a - 5a - 25)+25)
= √(a² - 25) + 25
= √(a² - 25 + 25)
= √(a²)
= |a|

There you go
The answer on the book is wrong, or just a typo.