nilai x yang memenuhi persamaaan |x+1|=|2x+3| adalah

(x + 1)² = (2x + 3)²
(x + 1) (x + 1) = (2x + 3) (2x + 3)
x² + x + x + 1 = 4x² + 6x + 6x + 9
x² + 2x + 1   =  4x² + 12x + 9
x² - 4x² + 2x - 12x + 1 - 9 = 0
-3x² - 10x - 8 = 0
- (3x² + 10x + 8) = 0
  6 x 4 = 24
  6 + 4 = 10
- (3x + 6) (3x + 4)
-------------------------
            3

= - (x + 2) (3x + 4) = 0
  (-x - 2) (3x + 4) = 0
  -x - 2 = 0   ∨   3x + 4 = 0
       -x = 2         3x = -4
        x = -2          x = -4/3

maaf ya bila salah^^...