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1C p19
Signed-off-by: szdytom <szdytom@qq.com>
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@ -399,7 +399,7 @@
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#exercise_sol(type: "explain")[
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#exercise_sol(type: "explain")[
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设
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令
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$ U = {(x, -x, 2x) in FF^3 : x in FF} quad "与" quad W = {(x, x, 2x) in FF^3 : x in FF} $
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$ U = {(x, -x, 2x) in FF^3 : x in FF} quad "与" quad W = {(x, x, 2x) in FF^3 : x in FF} $
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@ -462,3 +462,22 @@
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#tab 综上所述,“子空间求和”运算的加法单位元是 ${0}$,而只有 ${0}$ 有加法逆元。
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#tab 综上所述,“子空间求和”运算的加法单位元是 ${0}$,而只有 ${0}$ 有加法逆元。
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#exercise_sol(type: "answer")[
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证明或证伪:如果 $V_1$,$V_2$,$U$ 都是 $V$ 的子空间,且
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$ V_1 + U = V_2 + U $
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则有 $V_1 = V_2$。
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令
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$ V &= RR^3 \
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U &= {(0, x, y) in RR^3 : x,y in RR} \
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V_1 &= {0} \
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V_2 &= {(0, x, 0) in RR^3 : x in RR} $
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#tab 注意到 $V_1 + U = U = V_2 + U$,但 $V_1 != V_2$。
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#tab 该反例说明,题目中的命题不成立。
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