how 2*2 can be equal to 5?

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- February 2nd 2010, 11:20 PM #1

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- February 3rd 2010, 12:37 AM #2

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- February 3rd 2010, 12:47 AM #3
Hello afsanehIt's when you take the square root that you need to be careful. Just because , it doesn't necessarily mean that . It could be that .

It is true that , the line I've coloured red. This is because, when we evaluate the expressions in each bracket, the one on the LHS is and the one on the RHS is . Squaring each of these gives the same answer: . But that doesn't mean that they are equal, does it?

So remember: when you take a square root, remember the possible minus sign!

Grandad

- February 3rd 2010, 01:42 AM #4

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