b00m
Active Member
- Joined
- Nov 12, 2008
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- HSC
- 2010
- Uni Grad
- 2014
This question appeared in my 2 unit half-yearly.. and has since left me with a bit of a conundrum.
Typed it up in paint:
After applying your log laws and solving with algebra, your answers are x=5 and x=-1
but in this case, is the answer " x= -1" invalid?
If you test both answers, x=5 works fine, but x=-1 does not.... unless you move the '2' behind 'x' to make x². But is that a valid reason/explanation to obtain x=-1 as an answer?
I argued that you couldn't move the 2 behind the x as i thought that that would be incorrectly manipulating the question. A friend of mine, on the other hand, thought that both ansers (-1 and 5) were correct.
It's not a difficult question, i'm just unsure?
Typed it up in paint:

After applying your log laws and solving with algebra, your answers are x=5 and x=-1
but in this case, is the answer " x= -1" invalid?
If you test both answers, x=5 works fine, but x=-1 does not.... unless you move the '2' behind 'x' to make x². But is that a valid reason/explanation to obtain x=-1 as an answer?
I argued that you couldn't move the 2 behind the x as i thought that that would be incorrectly manipulating the question. A friend of mine, on the other hand, thought that both ansers (-1 and 5) were correct.
It's not a difficult question, i'm just unsure?
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