Question

Cari nilai "X"..
1.) X² + X - 20 = 0
2.) X² - X + 20 = 0
3.) X² + X + 20 = 0
4.) X² - X - 20 = 0

Pakai cara yerr.. :3

Answer 1

1. (x+5)(x-4) krn p + q = 1 dan jika p x q = -20
2 dan 3 maaf kakak tdk bs dikerjakan
4. (x - 5)(x + 4)

Answer 2

1.) x² + x - 20 = 0
     (x+5)(x-4) = 0
                   x = -5 atau x = 4

2.) x² - x + 20 = 0
     (x - (1/2))² = -20 + 1/4

         (x - (1/2)) = √(-79/4) atau (x - (1/2)) = -√(-79/4)
       (x - (1/2)) = (1/2)√-79 atau (x - (1/2)) = -(1/2)√-79
     (x - (1/2)) = (1/2).i.√79 atau (x - (1/2)) = -(1/2).i.√79
           x = (1/2)(1 + i.√79) atau x = (1/2)(1 - i.√79)

3.) x² + x + 20 = 0
      (x + (1/2))² = -20 + 1/4

         (x + (1/2)) = √(-79/4) atau (x + (1/2)) = -√(-79/4)
       (x + (1/2)) = (1/2)√-79 atau (x + (1/2)) = -(1/2)√-79
     (x + (1/2)) = (1/2).i.√79 atau (x + (1/2)) = -(1/2).i.√79
          x = (1/2)(-1 + i.√79) atau x = -(1/2)(1 + i.√79)

4.) x² - x - 20 = 0
     (x-5)(x+4) = 0
                   x = 5 atau x = -4