Find the product of sqrt (-15) and its conjugate.

Ok, so I am not sure how to do this with a square root involved. Any tips?

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- Sep 13th 2009, 12:14 PMtsmithConjugate?
Find the product of sqrt (-15) and its conjugate.

Ok, so I am not sure how to do this with a square root involved. Any tips? - Sep 13th 2009, 12:21 PMe^(i*pi)
- Sep 13th 2009, 12:22 PMskeeter
- Sep 14th 2009, 04:50 AMHallsofIvy
That must be a typo. The conjugate of $\displaystyle i\sqrt{15}$ is $\displaystyle -i\sqrt{15}$, of course. Generally speaking a product of conjugates, (a+bi)(a-bi)= $\displaystyle a^2+ b^2$ is the square of the "modulus" of the number. Since $\displaystyle |i\sqrt{15}|= |i||\sqrt{15}|= \sqrt{15}$, that product is 15.