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If A = [84105],B=[5-410-8] show that (A + B)2 = A2 + AB + B2

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प्रश्न

If A = `[(8, 4),(10, 5)], "B" = [(5, -4),(10, -8)]` show that (A + B)2 = A2 + AB + B2 

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उत्तर

(A + B)2 = A2 + AB + B
∴ (A + B)(A + B) = A2 + AB + B2
∴ A(A + B) + B(A + B) = A2 + AB + B2
∴ A2 + AB + BA + B2 = A2 + AB + B2
∴ `cancel("A"^2) + cancel("AB") + "BA" + cancel("B"^2) = cancel("A"^2) + cancel("AB") + cancel("B"^2)`
∴ BA = 0

We have to prove that
(A + B)2 = A2 + AB + B2,

i.e., to prove (A + B)(A + B) = A2 + AB + B

i.e., to prove A2 + AB + BA + B2 = A2 + AB + B2,

i.e., to prove BA = 0.

BA = `[(5, -4),(10, -8)] [(8, 4),(10, 5)]`

= `[(40 - 40, 20 - 20),(80  - 80, 40 - 40)]`

= `[(0, 0),(0, 0)]`

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अध्याय 4: Determinants and Matrices - Exercise 4.6 [पृष्ठ ९५]

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बालभारती Mathematics and Statistics (Arts and Science) Part 1 [English] Standard 11 Maharashtra State Board
अध्याय 4 Determinants and Matrices
Exercise 4.6 | Q 14 | पृष्ठ ९५

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