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May 5, 2016
Posted by **mikey** on Monday, December 3, 2012 at 10:22pm.

4x^2-4x+21=0

2)Find the standard form of the complex number.

8(cos pi/2 + i sin pi/2)

Thanks everyone!

- trigonometry -
**Reiny**, Monday, December 3, 2012 at 10:39pmx = (4 ± √(16 - 16(21)) )/8

= (4 ± √-320)/8

= (4 ± 8√-5)/8

= 1/2 ± i√5

x = 1/2 + i√5 or x = 1/2 - i√5

2)

8(cos π/2 + i sin π/2)

= 8(√2/2 + i √2/2)

= 4√2 + i (4√2)