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Prove that: aaaaaa|a2+2a2a+112a+1a+21331|=(a-1)3 - Mathematics

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प्रश्न

Prove that: `|("a"^2 + 2"a", 2"a" + 1, 1),(2"a" + 1, "a" + 2, 1),(3, 3, 1)| = ("a" - 1)^3`

योग
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उत्तर

 `|("a"^2 + 2"a", 2"a" + 1, 1),(2"a" + 1, "a" + 2, 1),(3, 3, 1)|`

[Applying R1 → R1 – R2 and R2 → R2 – R3]

=  `|("a"^2 - 1, "a" - 1, 0),(2"a" - 2, "a" - 1, 0),(3, 3, 1)|`

[Taking (a – 1) common from R1 and R2]

`("a" - 1)^2 |("a" + 1, 1, 0),(2, 1, 0),(3, 3, 1)|`

[Expanding along R3]

= `("a" - 1)^2 [1 * ("a" + 1) - 2]`

= (a – 1)3

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अध्याय 4: Determinants - Exercise [पृष्ठ ७८]

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एनसीईआरटी एक्झांप्लर Mathematics [English] Class 12
अध्याय 4 Determinants
Exercise | Q 9 | पृष्ठ ७८

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