# Simple Maths

((-6)^ 1/2 ) ( (-7)^1/2) = (42)^1/2

((-6)^ 1/2 ) ( (-7)^1/2) = (6^ 1/2 ) ( 7^1/2) ( i ^2)
= -(42)^1/2

Can anyone tell me where I did wrong?

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lurflurf
Homework Helper
frozen7 said:
((-6)^ 1/2 ) ( (-7)^1/2) = (42)^1/2

((-6)^ 1/2 ) ( (-7)^1/2) = (6^ 1/2 ) ( 7^1/2) ( i ^2)
= -(42)^1/2

Can anyone tell me where I did wrong?
((-6)^ 1/2 ) ( (-7)^1/2) = (42)^1/2
this step
$$x^zy^z=(xy)^z$$
is not true in general only when x,y>0

((-6)(-7))^(1/2)=(42)^(1/2)
(42)^(1/2)=(42)^(1/2)
should have left the right hand side alone

Thanks a lot..