7.设A,BsubsetR^n,且m^*B
设集合A=(a,b,c,d,e,f),A上的二元关系R=(,, ,,,,
1.讨论下列无穷积分是否收敛?若收敛,则求其值:-|||-(1) (int )_(0)^+infty x(e)^-(x^2)dx;-|||-(2) (int )
证明不等式:ln(1+e^x)-x>(1)/(e^x)+1,xin (-infty ,+infty ).证明不等式:$ln(1+e^{x})-x>\frac{1
6 设f(x)=|xsin^3x|e^cos x(-infty<+infty),证明函数f(x)在(-∞,+∞)内无界.6 (10分)设$f(x)=|x\sin
5.(1)若 ^3-(A)^2+2A-E=0, 证明A可逆,并求 A^(-1);-|||-(2)若 ^2-A-4E=0, 证明 A+E 可逆,并求 ((A+E)
令(x)=lim _(xarrow infty )dfrac (1-{e)^-ax}(1+{e)^-ax},则(x)=lim _(xarrow infty )d
练习 A,B均为三阶矩阵,满足AB+2A+B+E=0,若B=}1&2&01&2&01&2&1,则|A+E|=__
练习 A,B均为三阶矩阵,满足AB+2A+B+E=0,若 B}1&2&01&2&01&2&1,则|A+E|=__
(2)若 lim _(xarrow infty )((1+dfrac {k)(x))}^-3x=(e)^-1 ,则 k= __