作为线性空间$R^{3}$上的变换，下列$\cal A$不是线性变换的是（ ）。
A: $\cal {A}(a_{1},a_{2},a_{3})=(2a_{1}-a_{2}+a_{3},a_{2}-a_{3},2a_{1}+a_{3})$
B: ${\cal A}(a_{1},a_{2},a_{3})=(a_{1},0,a_{2})$;
C: ${\cal A}(a_{1},a_{2},a_{3})=(a_{1},2a_{2},3a_{3})$
D: ${\cal A}(a_{1},a_{2},a_{3})=(a_{1}^{2},a_{2}-a_{3},a_{3}^{2})$
A: $\cal {A}(a_{1},a_{2},a_{3})=(2a_{1}-a_{2}+a_{3},a_{2}-a_{3},2a_{1}+a_{3})$
B: ${\cal A}(a_{1},a_{2},a_{3})=(a_{1},0,a_{2})$;
C: ${\cal A}(a_{1},a_{2},a_{3})=(a_{1},2a_{2},3a_{3})$
D: ${\cal A}(a_{1},a_{2},a_{3})=(a_{1}^{2},a_{2}-a_{3},a_{3}^{2})$
举一反三
- 下列多项式在有理数域上不可约的是（ ）。 A: $(x-a_{1})(x-a_{2})...(x-a_{n})-1$，其中$a_{1},a_{2},...,a_{n}$是两两互异的整数； B: $(x-a_{1})(x-a_{2})...(x-a_{n})+1$，其中$a_{1},a_{2},...,a_{n}$是两两互异的整数； C: $(x-a_{1})^{2}(x-a_{2})^{2}...(x-a_{n})^{2}+1$，其中$a_{1},a_{2},...,a_{n}$是两两互异的整数； D: $(x-a_{1})^{2}(x-a_{2})^{2}...(x-a_{n})^{2}-1$，其中$a_{1},a_{2},...,a_{n}$是两两互异的整数.
- 将向量组`a_{1}=(1,1)^{T}`,`a_{2}=(1,-2)^{T}`施密特正交化为向量组
- 与向量`a_{1}=(1,1,1)^{T}`,`a_{2}=(1,-2,1)^{T}`正交的向量为
- 若根号a有意义,则a_；当a_时,根号负a无意义
- 10. 数列和级数的收敛性验证是高等数学中的两个非常重要的问题，使用图形的方法是发现结论的最直观方法，实际上只要将数列（或者部分和数列）的前面一些项在图形上画出来并看看是否有收敛于某值的趋势。数列`{a_{n}}`收敛. 其中`a_{n}=0.5(a_{n-1}+{5}/{a_{n-1}}),a_{1}=28`