Question

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Which of the following is a solution of x2 + 4x + 25?
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Answer 1

2 + i square root of 21

−2 + i square root of 84

−2 + i square root of 21

−2 + i square root of 84

Answer 2

For this, we;ll use the quadratic formula. Do you recall what it is?

Answer 3

Yes, -b square root of b^2 - 4ac over 2a

Answer 4

OK. Now you want to plug in a, b, and c

Answer 5

\[\frac{-4±\sqrt{4^2-4*1*25}}{2*1}\]

Answer 6

okay...-4 +- 16 - 100
over
2
?

Answer 7

the square root of 16-100, which is the square root of -84, or 2isqrt(21).

Answer 8

so we have (-4±2isqrt(21))/2

Answer 9

canceling the 2's,we get -2±isqrt(21)

Answer 10

or choice C

Answer 11

Ohh, cool, I see how you got that!
thanks for your help:-)