在同一个图上,画出满足下列条件的 y=∣2x−p∣y = |2x - p| 和 y=qxy = qx 的图像草图,标出轴交点。
  • pp 和 qq 是常数,p>1p > 1 且 q>0q > 0,以及
  • 图像仅有一个交点。

  1. (a)

    写出 qq 的最小值。

  2. (b)

    解不等式 ∣2x−p∣>qx|2x - p| > qx,用 pp 和 qq 表示你的答案。

先不看答案,让 AI 诊断你卡在哪里?

它不会直接告诉你答案,而是问你卡在哪一步看看 AI 是怎么陪你一步步弄懂这道题的

完整解法

2(a)

1. Determine the condition for exactly one intersection by analyzing the gradients.

The graph of y=∣2x−p∣y = |2x - p| is V-shaped. Its right branch is defined by the line y=2x−py = 2x - p (for x≥p2x \ge \frac{p}{2}) and has a gradient of 22.
Since the line y=qxy = qx passes through the origin (0,0)(0,0) and q>0q > 0, it will naturally intersect the left branch y=−2x+py = -2x + p exactly once.
To ensure there is only one point of intersection in total, y=qxy = qx must not catch up to and intersect the right branch. This requires the line y=qxy = qx to be parallel to or steeper than the right branch:
q≥2q \ge 2
Therefore, the least possible value for qq is 22.

答案

22

2(b)

1. Find the $x$-coordinate of the single point of intersection.

Based on the graphs sketched earlier, the line y=qxy = qx starts at (0,0)(0,0) and must intersect the left branch of the VV-shaped modulus graph, which has the equation y=−(2x−p)=p−2xy = -(2x - p) = p - 2x.
Since it is given that there is only one point of intersection, we solve for xx on this branch:
p−2x=qxp - 2x = qx
qx+2x=pqx + 2x = p
x(q+2)=px(q + 2) = p
x=pq+2x = \frac{p}{q + 2}

2. Determine the solution to the inequality using the intersection point.

The inequality ∣2x−p∣>qx|2x - p| > qx is satisfied wherever the graph of y=∣2x−p∣y = |2x - p| lies strictly above the line y=qxy = qx.
At x=0x = 0, the modulus graph is at y=py = p (where p>1p > 1), while the line is at y=0y = 0. Thus, the modulus graph starts out above the line.
It remains above the line until they meet at the single intersection point. Since there are no other intersections, the modulus graph is only above the line to the left of this point.
Therefore, the solution is:
x<pq+2x < \frac{p}{q + 2}

答案

x<pq+2x < \frac{p}{q + 2}

AI 分析,可能出错

用 AI 批改,圈出写错的那一步,并自动将你的薄弱点存入错题本,形成你的错因库。

同一知识点的其他题

  1. 1已知函数y=f(x)y=f(x)是定义在RR上的偶函数,且在区间[0,+∞)[0,+\infty)上单调递增,若实数mm满足f(log⁡3m)⩾f(1)f({{\log}_{3}}m)\geqslant f(1),则mm的取值范围为___.
  2. 2在同一幅图中,画出 y=∣2x+3∣y = |2x + 3| 和 y=−2x2−8x−3y = -2x^2 - 8x - 3 的图像。 (你不需要标出任何轴交点和驻点。) 精确求解不等式 ∣2x+3∣>−2x2−8x−3|2x + 3| > -2x^2 - 8x - 3。
  3. 3求 ∫3ex5−0.3ex dx\displaystyle \int \frac{3e^x}{5 - 0.3e^x} \, dx ∫cos⁡(ln⁡x) dx\displaystyle \int \cos(\ln x) \, dx,其中 x>0x > 0 ∫03∣2ex−5∣ dx\displaystyle \int_0^3 |2e^x - 5| \, dx…
  4. 4已知函数f(x)=x2−ax(a≠0)f(x)=x^{2}-ax(a\neq 0),g(x)=ln⁡xg(x)=\ln x,f(x)f(x)图象与xx轴异于原点的交点MM处的切线为l1l_{1},g(x−1)g(x-1)与xx轴的交点NN处的切线为…
  5. 5用数学归纳法证明,对于所有正整数 nn 以及 x∈Rx\in\mathbb{R},x≠0, x≠1x\ne 0,\ x\ne 1, 1x−1−1x−1x2−⋯−1xn=1xn(x−1) .\frac{1}{x-1}-\frac{1}{x}-\frac{1}{x^2}-\dots-\frac{1}{x^n}=\frac{1}{x^n(x-1)}\,.…