帮我用中文解析这五个题目，并且生成解说视频---**Question 5**
**Question Stem:**
设函数 f(x) 定义在 R 上且周期为 2 的偶函数. 当 2≤x≤3 时, f(x)=5-2x, 则 f(-3/4)=
**Options:**
A. -1/2
B. 1/4
C. 1/2
D. 1/4
**Question 6**
**Question Stem:**
帆船比赛中, 运动员可借助风力计测定风速的大小和方向, 测出的结果在航海学中称为视风速. 视风速对应的向量, 是真风风速对应的向量与船行风速对应的向量之和, 其中船行风速对应的向量与船速对应的向量大小相等, 方向相反. 图 1 给出了部分风力等级、名称与风速大小的对应关系. 已知某帆船运动员在某时刻测得的视风风速对应的向量与船速对应的向量如图 2 (风速的大小和向量的大小相同, 单位 m/s), 则真风为
**Table (Figure 2):**
| 等级 | 风速大小 | 名称 |
|---|---|---|
| 2 | 1.1~3.3 | 轻风 |
| 3 | 3.4~5.4 | 微风 |
| 4 | 5.5~7.9 | 和风 |
| 5 | 8.0~10.1 | 强风 |
**Chart (Figure 1):**
Type: 2D Cartesian coordinate system with vectors.
Axes:
X-axis labeled "船速" (Ship Speed). Scale 0 to 3.
Y-axis labeled "视风风速" (Apparent Wind Speed). Scale 0 to 3.
Elements:
Origin O at (0,0).
Vector from O to (3, 3) labeled "视风风速". This represents the apparent wind velocity vector.
A point at (3, 0) labeled "船速". This indicates the magnitude of the ship speed is 3 m/s.
Based on the problem description and diagram, it seems the apparent wind vector is (3, 3), and the ship velocity vector magnitude is 3 along the positive x-axis. The "船行风速对应的向量" is equal in magnitude and opposite in direction to the "船速对应的向量". Assuming the ship velocity vector is (3, 0) (magnitude 3 in the positive x direction, although the label is on the x-axis representing magnitude), the "船行风速对应的向量" (velocity of ship relative to air) would be (-3, 0).
The equation is: 视风速 vector = 真风风速 vector + 船行风速 vector.
So, 真风风速 vector = 视风风速 vector - 船行风速 vector.
From the chart, 视风风速 vector = (3, 3). Assuming ship velocity vector is (3, 0), then 船行风速 vector = (-3, 0).
真风风速 vector = (3, 3) - (-3, 0) = (6, 3).
Magnitude of 真风风速 = |(6, 3)| = sqrt(6^2 + 3^2) = sqrt(36 + 9) = sqrt(45) = 3√5.
Approximate value: 3 * 2.236 = 6.708 m/s.
Looking up 6.708 m/s in the table (Figure 2), it falls into the range 5.5~7.9 m/s, which corresponds to "和风".
**Options:**
A. 轻风
B. 微风
C. 和风
D. 强风
**Question 7**
**Question Stem:**
若圆 x² + (y+2)² = r² (r>0) 上到直线 y = √3x + 2 的距离为 1 的点有且仅有 2 个, 则 r 的取值范围是
**Options:**
A. (0, 1)
B. (1, 3)
C. (3, +∞)
D. (0, +∞)
**Question 8**
**Question Stem:**
若实数 x, y, z 满足 2 + log_e x = 3 + log_e y = 5 + log_e z, 则 x, y, z 的大小关系不可能是
**Options:**
A. x > y > z
B. x > z > y
C. y > x > z
D. y > z > x