Question

Evaluate: `|("a" - "b" - "c", 2"a", 2"a"),(2"b", "b" - "c" - "a", 2"b"),(2"c", 2"c", "c" - "a" - "b")|`

Answer 1

We have, `|("a" - "b" - "c", 2"a", 2"a"),(2"b", "b" - "c" - "a", 2"b"),(2"c", 2"c", "c" - "a" - "b")|`

[Applying R₁ → R₁ + R₂ + R₃]

= `|("a" + "b" + "c", "a" + "b" + "c", "a" + "b" + "c"),(2"b", "b" - "c" - "a", 2"b"),(2"c", 2"c", "c" - "a" - "b")|`

[Taking (a + b + c) common from the first row]

= `("a" + "b" + "c")|(1, 1, 1),(2"b", "b" - "c" - "a", 2"b"),(2"c", 2"c", "c" - "a" - "b")|`

[Applying C₁ → C₁ – C₃ and C₂ → C₂ – C₃]

= `("a" + "b" + "c")|(0, 0, 1),(0, -("a" + "b" + "c"), 2"b"),("a" + "b" + "c", "a" + "b" + "c", "c" - "a" - "b")|`

Expanding along R₁,

= (a + b + c) [1 × 0 + (a + b + c)²]

= (a + b + c)³