Akar-akar persamaan x² + ( a - 1 )x + 21 = 0 adalah α dan β dengan α , β positif. Jika α = β + 4, nilai .....

langsung aja ya

alfa + beta = -b/a = -(a+1)/1 = -(a+1)
alfa + beta = -(a+1)
karna diketahui alfa = beta + 4

beta + 4 + beta = -(a+1)
2beta = -(a+1) - 4
2beta = -a - 5
beta = -(a+5)/2

alfa = beta + 4
alfa = -(a+5)/2 + 4
alfa = -(a+5)/2 + 8/2
alfa = -(a - 3)/2


alfa×beta = c/a = 21/1 = 21

alfa×beta = 21
-(a - 3)/2 × -(a + 5)/2 = 21
(a - 3)(a + 5) = 21 × 2 × 2
a^2 + 2a - 15 = 84
a^2 + 2a -99 = 0
(a + 11)(a - 9) = 0
a = -11 dan a = 9

krn alfa dan beta positif
yg memenuhi a = -11