persamaan kuadrat x2 + (p+1)x - 18 = 0 mempunyai akar-akar a dan b. jika a + 2b = 0 dan p>0, nilai p yang memenuhi adalah

jawab

a = 1
b = p+1
c = -18

α+β = -b/a = - (p+1) = -p-1
α. β  = c/a = -18
α + 2β = 0 --> α= - 2β

α. β = -18
-2β² = -18
β² = 9
β = 3  atau β = -3

β = 3 --> α = - 2β = - 6
β = - 3 --> α = - 2β = 6

α + β = - p - 1
(-6)+(3) = -p - 1
- 3 = - p + 1
p = 1+3 
p = 4