8.下列各组函数表示同一函数的是( )
A. | f(x)=|x|,g(x)=$\left\{\begin{array}{l}{x(x≥0)}\\{-x(x<0)}\end{array}\right.$ | B. | f(x)=$\frac{{x}^{2}-4}{x-2}$,g(x)=x+2 | ||
C. | f(x)=$\sqrt{{x}^{2}}$,g(x)=x+2 | D. | f(x)=$\sqrt{1-{x}^{2}}$+$\sqrt{{x}^{2}-1}$,g(x)=0,x∈{-1,1}. |
7.在等差数列{an}中,Sp=q,Sq=q,Sp+q的值为( )
A. | p+q | B. | -(p+q) | C. | p2-q2 | D. | p2+q2 |
3.已知定义在R上的函数f(x)满足f(x)=f(2-x),其图象经过点(2,0),且对任意x${\;}_{{1}_{\;}}$,x2∈(1,+∞),且x1≠x2,(x1-x2)[f(x1)-f(x2)]>0恒成立,则不等式(x-1)f(x)≥0的解集为( )
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A. | (-∞,1] | B. | [1,+∞) | C. | (-∞,0]∪[1,2] | D. | [0,1]∪[2,+∞) |