5.已知x,y满足$\left\{\begin{array}{l}{x≥0}\\{x+y-5≤0}\\{2x-y-1≤0}\end{array}\right.$,则z=mx+y(0<m<1)的最大值是( )
| A. | -1 | B. | 5 | C. | 7 | D. | 2m+3 |
4.运行如图所示的程序框图,则输出的S的值为( )

| A. | -10 | B. | -7 | C. | 9 | D. | 12 |
2.已知角α的终边经过点P(1,2),则cos2α等于( )
| A. | -$\frac{3}{5}$ | B. | $\frac{1}{5}$ | C. | $\frac{\sqrt{5}}{5}$ | D. | $\frac{3}{5}$ |
1.已知复数z=$\frac{1-i}{i}$,则|z|等于( )
| A. | 1 | B. | $\sqrt{2}$ | C. | 2 | D. | 2$\sqrt{2}$ |
19.已知角α的终边经过点P(3a,4a),其中a≠0,则sinα-cosα=( )
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| A. | $\frac{1}{5}$ | B. | $\frac{7}{5}$ | C. | ±$\frac{1}{5}$ | D. | ±$\frac{7}{5}$ |