Analyzing the Setup
We are tasked with finding the area of a region defined by three distinct inequalities:
2y≤x2+3, y+∣x∣≤3, and y≥∣x−1∣.
This is a classic JEE Advanced problem that tests your ability to translate algebraic constraints into a physical, bounded shape.
The Canvas
Imagine standing on the Cartesian plane. We have three 'fences' enclosing our territory:
1. The first, y≤2x2+3, is an upward-opening parabola.
2. The second, y≤3−∣x∣, is a downward-pointing V-shape with a peak at (0,3).
3. The third, y≥∣x−1∣, is an upward-pointing V-shape with its vertex at (1,0).
The first step is to find the 'vertices' of our region—the points where these curves intersect. By solving the equations y=3−∣x∣ and y=∣x−1∣, we find the intersection points at (2,1) and (−1,2). These are the anchors of our region.
The Boundary Shift
Is the upper boundary the same throughout the entire region? Let's check the intersection of the parabola y=2x2+3 and the line y=3−∣x∣.
For x≥0, setting 2x2+3=3−x leads to x2+2x−3=0, which gives us x=1.
This is a critical realization! At x=1, the parabola and the line meet. Before x=1, the parabola is the 'ceiling' of our region. After x=1, the line y=3−x becomes the 'ceiling.'
Because the ceiling changes, we cannot use a single integral. We must split our journey into two parts.
The Integration
We define our total area A as the sum of two regions: A1 (from x=−1 to x=1) and A2 (from x=1 to x=2).
For A1, the upper bound is the parabola 2x2+3 and the lower bound is the line y=1−x. The integral becomes:
A1=∫−11(2x2+3−(1−x))dx
Simplifying this, we get:
A1=∫−11(2x2+x+21)dx=[6x3+2x2+2x]−11=34
Now for A2, the region from x=1 to x=2. Here, the upper bound is y=3−x and the lower bound is y=x−1. The integral is:
A2=∫12((3−x)−(x−1))dx=∫12(4−2x)dx
Calculating this, we find:
A2=[4x−x2]12=(8−4)−(4−1)=1
Final Calculation
We have our two pieces: A1=34 and A2=1. Adding them together, the total area is:
The question asks for 6A. Thus:
We have navigated the curves, respected the boundaries, and arrived at the solution. Remember, in JEE Advanced, the math is just the language; the true skill is in the visualization.