Solution
Related Formula
For a continuous function f(x):
- A point x = c is a local minimum if f(x) changes from decreasing to increasing as x passes through c (i.e., a trough in the graph).
- A point x = c is a local maximum if f(x) changes from increasing to decreasing as x passes through c (i.e., a peak in the graph).
Core Logic
Let's analyze g(x) = |x+2| - 2|x| first to construct f(x) = |g(x)|.
- If x ≤ -2:
- If -2 < x ≤ 0:
- If x > 0:
Now, we find the critical transition points where g(x) = 0:
- x - 2 = 0 x = 2 (not in x ≤ -2)
- 3x + 2 = 0 x = -2/3 (lies in -2 < x ≤ 0)
- -x + 2 = 0 x = 2 (lies in x > 0)
Thus, the absolute value function f(x) = |g(x)| transitions at x = -2, x = -2/3, x = 0, and x = 2.
Step 1: Graph Reconstruction and Critical Points Analysis
Evaluating values at these boundaries:
- f(-2) = | |-2+2| - 2|-2| | = |0 - 4| = 4
- f(-2/3) = 0 (trough, local minimum)
- f(0) = | |2| - 0 | = 2 (peak, local maximum)
- f(2) = 0 (trough, local minimum)
- For x < -2, f(x) = |x-2| = 2-x, which decreases towards 4 as x → -2.
- At x = -2, there is a corner point (-2,4), but it is not an extremum because the function continues to decrease to 0 on the right.
- At x = -2/3, it reaches 0 and turns upwards (local minimum).
- At x = 0, it reaches a local peak of 2 and turns downwards (local maximum).
- At x = 2, it reaches 0 and turns upwards (local minimum).
Let's trace the graph:
Step 2: Calculating m + n
From the verified graph and transition behaviors:
- Local minima points (m): x = -2/3 and x = 2 m = 2
- Local maxima points (n): x = 0 n = 1
Pattern Recognition
Whenever you have f(x) = |g(x)| where g(x) is continuous:
- Any point where g(x) = 0 becomes a local minimum with value 0 (unless it was a tangent point already, which still remains a minimum).
- Corners of the original absolute segments like x=0, -2 must be checked sequentially for slope changes.
Chapter Mix
Class 12 Mathematics: Limits, Continuity and Differentiability Class 11 Mathematics: Relations and Functions