plz explain plz

[akmkat_bd]

I'm not well in mathematics. However, may be, It will not require so much of it. But everytime I get confused when I think about it,

(-1)(-1) = (-1)^2 = 1 = 1^2

so, (-1)^2 = 1^2

then, -1 = 1

what's the matter with this proof? plz someone help.

[Zoijar]

Well, as you noticed now, you can't just take square roots and expect the sign to be alright. Therefore, when you take square roots, you have to make the value under it absolute. Ie. (-1)^2=1^2 <=> |-1|=|1|

[Naseer Asif]

Hi akmkat bd!

There are other ways to show -1=1,

e.g. Consider -1/1=1/-1

now taking square root on both sides, we have

=> Sqrt[-1/1]=Sqrt[1/-1]

=> Sqrt[-1]/Sqrt[1]=Sqrt[1]/Sqrt[-1]

now by cross multiplying, we have

=> Sqrt[-1] Sqrt[-1]=Sqrt[1] Sqrt[1]

=> Sqrt[-1]^2=Sqrt[1]^2

=> -1=1