Jika akar-akar persamaan kuadrat x^2 - cx + 20 = 0 dua lebih besar daripada akar-akar persamaan kuadrat x^2 - 5x + d = 0, nilai c + d adalah

[tex] {x}^{2} - cx + 20 = 0 \: (x1 + 2) \: (x2 + 2) \\ x1 + x2 + 4 = c \: > > 5 + 4 = c = 9 \\ x1x2 + 2(x1 + x2) + 4 = d + 2(5) + 4 = 20 \: > > d = 6 \\ {x}^{2} - 5x + d = 0 \: (x1) \: (x2) \\ x1 + x2 = 5 > > x1 \times x2 = d \\ c + d = 9 + 6 = 15[/tex]