00:02
Given in this question is a equals to aij, b a square matrix of order n, such that aij is equal to 0, if i is less than j, then a matrix is a11, 0, and so on, 0, a21, a2, 0, and so on, 0, a2, a2, 0, 0 and so on to 0 a 3 1 a 3 2 a 3 2 a 3 3 0 and up to 0 similarly an 1 a n 2 a n 3 and 4 up to a n n now since there are n minus 1 0 expanding the determinant of a by 1 row we have determinant of a equals to a11, 0, 0 to 0 to 0, a21, a22, 0 up to 0, a31, a2, a31, a32, a32, a33, 0 up to 0, an1, an1, a2, an2, an3, a3, a3, an4, up to a &n now equals to a11 times of determinant a22002, a32, a333 up to 0, a3n2, an2, an2, an3, a3, a3, an4, up to 0, again expanding the determinant by first row we have determinant a equals to a11 multiplied by a 2 2 times of determinant a 3 3 0 up to 0 an3 an3 an4 0 up to 0 an 3 an3 an4 0 up to 0 an 3 an3, an4 up to annn by ann 4 up to ann.
04:07
By continuing the determinant expansion n minus 2 times, we get determinant of a equals to a11 multiplied by a22 multiplied by a33 up to ann...