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prove that `|[1,a,b+c],[1,b,c+a],[1,c,a+b]|=0` |
Answer» The given determinant `=|{:(1, a, b+c), (1, b, c+a), (1, c, a+b):}|` `=|{:(1, a, a+b+c), (1, b, a+b+c), (1, c, a+b+c):}| " "["applying "C_(3) to C_(3) + C_(2)]` ` =(a+b+c) * |{:(1, a, 1), (1, b, 1), (1, c, 1):}| ["taking (a+b+c) common from "C_(3)]` ` = (a+b+c) xx 0 = 0 " "[because C_(1) "and "C_(3) " are identical"].` |
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