JEE MainMathematicsArea Under the CurvesMCQ+4 / −1
Let the area of the region be . Then is equal to :
- A14
- B18
- C16
- D12
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Correct answer: A
We need the area of the region satisfying
So the region is
Thus, for each , the allowed lies between
We now determine where this is possible.
1. Compare the two upper bounds
We compare
Solve
This gives
Let . Then
Hence
So:
- for , upper bound is ,
- for , upper bound is .
2. Find where lower bound does not exceed upper bound
We need
We check in intervals.
Case I:
Here upper bound is . Also, since ,
Need
Multiply by :
which is always true. So all work.
Case II:
Here upper bound is and
Need
So work.
Case III:
Here upper bound is (since ), and
Need
Together with , this gives only . So no interval contribution from left side beyond the endpoint.
Hence the region exists for
3. Set up area integral
So
Simplify integrands.
For :
For :
Thus
4. Evaluate the integrals
First integral
Let . When , ; when , .
=\frac12\left[\frac{u^3}{3}\right]_0^2 =\frac12\cdot \frac{8}{3}=\frac{4}{3}.$$ ### Second integral $$\int_1^2 (4-2x)\,dx = [4x-x^2]_1^2=(8-4)-(4-1)=4-3=1.$$ So $$A=\frac{4}{3}+1=\frac{7}{3}.$$ Therefore, $$6A=6\cdot \frac{7}{3}=14.$$ --- ## 5. Check options - A: $14$ ✅ - B: $18$ ❌ - C: $16$ ❌ - D: $12$ ❌ So the correct option is **A**.More from Area Under the Curves
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