0.     Objective

   How we can distinguish between1) A Real root and 2) an imaginary root

1.     Definition

1)    The real number of the quadratic equation called real root

2)    A complex number is not a real number

2.     Mathematical proof

   b2 – 4ac >0 = 1) 

when you put the number in b2 – 4ac , if the answer is positive that will be a real number

   b2 – 4ac <0 = 2)= 

when you put the number in b2 – 4ac , if the answer is negative that will be an imaginary number

3.     Solving Problems

(1)   x2 + x – 5 =0           (2) x2 - 2x + 3 =0

a = 1, b = 1, c = -5      a = 1, b = - 2, c = 3

= (real root)        1(imaginary root)

4.     Vocabulary

     근의 공식 - quadratic formula

      루트 - The name of the symbol √ that represents the square root.

 근 - The value of the unknown that satisfies the equation.

5.     Other Information

       https://terms.naver.com/entry.nhn?docId=3582427&cid=60204&categoryId=60204

       who made Formula of root