diketahui P dan q akar-akar dari persamaan x ^2 +( 2a + 1) x + 20 = 0 Jika p<0,q< 0 dan q–p = 1 nilai 2a adalah

x² + (2a +1) x + 20 =0
a= 1
b = 2a + 1
c = 20


p + q = -b/a
p + q = - (2a +1) .....(i)

p q = c./a
p q = 20 --> q = 20/p .....(ii)

q - p = .1 .
20/p - p= 1 ....kalikan p
20 - p² = p
p² + p - 20 =0
(p + 5)(p -4) =0
p = -5 atau p = 4
p< 0 -->p = - 5

q - p = - 1
q = p - 1
q = - 5 - 1
q = - 6

p + q= - (2a + 1)
-5 - 6 = - (2a + 1)
11 = 2a + 1
2a = 10
a= 5