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If a=(1)/(sqrt(10))(3hati+hatk) and b=(1)/(7)(2hati+3hatj-6hatk), then the value of (2a-b).[(axxb)xx(a+2b)] is |
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Answer» `-3` `:. (2a-b) .[(a xx b) xx (a+2B)]` `= (2a - b).{(a xx b)xx a + (a xx b) xx 2b }` `= (2a - b) .{(a.a) b - (b.a) a+ 2 (a.b) b - 2(b.b)a}` `= (2a - b) .{1(b)- (0) a + 2(0) b - 2 (1)a}` [ `:' a .b = 0` and ` a.a = b = 1`] `= (2a - b) (b - 2a) = - (4|a|^(2) - 4A. b + |b|^(2))` `= - {4 - 0 + 1} = - 5` |
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