Question

Matrix A = `[(1, 2, 3),(1, 1, 5),(2, 4, 7)]` then the value of a₃₁ A₃₁ + a₃₂ A₃₂ + a₃₃ A₃₃ is ______.

Options

• 1

• 13

• –1

• –13

Answer 1

Matrix A = `[(1, 2, 3),(1, 1, 5),(2, 4, 7)]` then the value of a₃₁ A₃₁ + a₃₂ A₃₂ + a₃₃ A₃₃ is –1.

Explanation:

Here A = `[(1, 2, 3),(1, 1, 5),(2, 4, 7)]` 

we know that,

a₃₁ A₃₁ + a₃₂ A₃₂ + a₃₃ A₃₃ = |A|

= +1(7 – 20) – 2(7 – 10) + 3(4 – 2)

= – 13 + 6 + 6

= – 1