JIKA KURVA f(x)=x^2-mx+5 menyinggung garis 2x-y+1=0 maka nilai m?

2x - y + 1 = 0
2x + 1 = y
y = 2x + 1
y = y
x² - mx + 5 = 2x + 1
x² - mx - 2x + 5 - 1 = 0
x² - (m+2)x + 4 = 0
menyinggung maka D = 0
b² - 4ac = 0
(m+2)² - 4(1)(4) = 0
m² + 4m + 4 - 16 = 0
m² + 4m - 12 = 0
(m + 6)(m - 2) = 0
m = -6 atau m = 2