Question

Find the value of discriminant for each of the following equations. 

i. 2y² – y + 2 = 0 

ii. 5m² – m = 0 

iii. √5 x² – x – √5 = 0

Answer 1

i. 2y² – y + 2 = 0

Comparing the above equation with ay² + by + c = 0, we get 

a = 2, b = -1, c = 2 

∴ b² – 4ac = (-1)² – 4 × 2 × 2 

= 1 – 16 

∴ b² – 4ac = -15

ii. 5m² – m = 0 

∴ 5m² – m + 0 = 0 

Comparing the above equation with am² + bm + c = 0, we get 

a = 5, b = -1, c = 0 

∴ b² – 4ac = (-1)² – 4 × 5 × 0 

= 1 – 0 

∴ b² – 4ac = 1

iii. √5x – x – √5 = 0 

Comparing the above equation with ax² + bx + c = 0, we get 

a = √5, b = -1, c = -√5 

∴ b² – 4ac = (-1)² – 4 × √5 × √5

= 1 + 20 

∴ b² – 4ac = 21