Repeated roots mean d = 0.

d = b² – 4ac

d = (4)² – 4 (9) (6)

d = 16 – 216

d = –200

∴ roots are not repeated.

Repeated roots mean d = 0.

d = b² – 4ac

d = (–12)² – 4(9)(4)

d = 144 – 144

d = 0

Yes, roots are repeated.

Repeated roots mean d = 0.

d = b² – 4ac

d = (–6)² – 4(1)(6)

d = 36 – 24

d = 12

∴ roots are not repeated.

Repeated roots mean d = 0.

d = b² – 4ac

d = (–40)² – 4 (16) (25)

d = 1600 – 1600

d = 0

∴ roots are repeated.