Complex Numbers and Discriminants

Question

0

775

1

+279

Which of the following are solutions to the equation below?

Check all that apply.

x² + x - 5 = 0

A. \(x = {5 - \sqrt{21} \over 2}\)

B. \(x = {5 + \sqrt{21} \over 2}\)

C. \(x = {5 + \sqrt{29} \over 2}\)

D. \(x = {-1 - \sqrt{21} \over 2}\)

E. \(x = {5 - \sqrt{29} \over 2}\)

F. \(x = {-1 + \sqrt{21} \over 2}\)

CreatorRozen Oct 14, 2019

CPhill · Answer 1 · 2019-10-14T03:11:53

x^2 + x - 5 = 0

Let a = 1 b = 1 c = -5

Using the quadratic formula we have that

x = -1 ±√ [ 1^2 - 4* 1 * -5 ] = -1 ± √ [1 + 20 ] -1 ± √21

___________________ _____________ = ________

2 * 1 2 2

So D, F are the correct answers