grafik fungsi kuadrat y = f(x) memotong sumbu X di (–1, 0) dan (5, 0), serta melalui titik (1, 8), jadi nilai f(–2) =
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Tipot Sumbu - x = ( - 1 , 0 ) dan ( 5 , 0 )
x1 = - 1
y1 = 0
x2 = 5
y2 = 0
(x - x1) (x - x2) = 0
(x + 1) (x - 5) = 0
x² - 5x + x - 5 = 0
x² - 4x - 5 = 0
f(-2)
= (-2)² - 4(-2) - 5
= 4 + 8 - 5
= 12 - 5
= 7
