I have a quick basic question , perhaps Arildno could could help me as he was very good at explaining before.....(adsbygoogle = window.adsbygoogle || []).push({});

2 + root 9 = 5

If I add or subtract or multiply by a number , the equality holds as long as its done to both sides but if I square both sides it means I multiply one side by

(2 + root 9 ) while I multiply the other side by 5.

But nevertheless, the equality clearly remains valid.

Why is this ?

Thanks

Roger

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# Subtract or multiply by a number

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