|x kuadrat - 4x-12||=9 tolong kerjakan!!!

Bab Nilai Mutlak
Matematika SMA Kelas X

|x² - 4x - 12| = 9

x² - 4x - 12 = 9
x² - 4x - 12 - 9 = 0
x² - 4x - 21 = 0
(x - 7) (x + 3) = 0
x - 7 = 0     atau      x + 3 = 0
x = 7                        x = -3

x² - 4x -12 = -9
x² - 4x - 12 + 9 = 0
x² - 4x - 3 = 0
a = 1; b = -4; c = -3

x₁₂ = (-b +- √(b² - 4ac))/2a
x₁₂ = (- (-4) +- √((-4)² - 4 . 1 . (-3)))/(2 . 1)
x₁₂ = (4 +- √(16 + 12))/2
x₁₂ = (4 +- √28)/2
x₁₂ = (4 +- 2√7)/2
x₁₂ = 2 +- √7

x₁ = 2 + √7
x₂ = 2 - √7

HP = { -3, 2 - √7, 2 + √7, 7 }