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# C3 Help - Really easy! watch

1. The price of a computer system can be modelled by the formula:

When will it be worth less than £200?

I did:

The answer is 4.28, so I'm doing it right, but why am I getting a negative? Thanks!

Edit: Is it because I forgot to inverse 2/17 into 17/2, when I removed the - from the t - that gives me the right answer. Sorry guys - but is this right?
2. If it's easy, you would do it.
3. (Original post by Narik)
The price of a computer system can be modelled by the formula:

When will it be worth less than £200?

I did:

The answer is 4.28, so I'm doing it right, but why am I getting a negative? Thanks!

Edit: Is it because I forgot to inverse 2/17 into 17/2, when I removed the - from the t - that gives me the right answer. Sorry guys - but is this right?
yeah, you need to use 17/2.

when you have e^ (-t/2) > 2/17

it's 1/ e^(t/2) > 2/17

when you flip it you get e ^ (t/2) = 17/2
4. (Original post by Jingers)
If it's easy, you would do it.
The mistake I was making was simple - so finding out where I went wrong wasn't hard.

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