Mathematics · Area under the Curves

JEE Main 2026 — 24 January, Evening Shift — Question 12

Let f(α)f(\alpha) denote the area of the region in the first quadrant bounded by x=0,x=1,y2=x\mathrm{x}=0, \mathrm{x}=1, \mathrm{y}^{2}=\mathrm{x} and y=∣αx−5∣−∣1−αx∣+αx2\mathrm{y}= |\alpha \mathrm{x}-5|-|1-\alpha \mathrm{x}|+\alpha \mathrm{x}^{2}. Then (f(0)+f(1))(\mathrm{f}(0)+\mathrm{f}(1)) is equal to :

  1. Option A:

    99

  2. Option B:

    1414

  3. Option C:

    77

    Correct
  4. Option D:

    1212

Answer: C

Step-by-step solution

at α=0⇒f(0)\alpha=0 \Rightarrow \mathrm{f}(0)

x=0,x=1,y2=x\mathrm{x}=0, \mathrm{x}=1, \mathrm{y}^{2}=\mathrm{x}

y=∣0⋅x−5∣−∣1−0⋅x∣+0⋅x2\mathrm{y}=|0 \cdot \mathrm{x}-5|-|1-0 \cdot \mathrm{x}|+0 \cdot \mathrm{x}^{2}

y=4\mathrm{y}=4

A1=∫01(4−x)dxA_{1}=\int_{0}^{1}(4-\sqrt{x}) d x

=4x−x3232∣01=4 x-\left.\frac{x^{\frac{3}{2}}}{\frac{3}{2}}\right|_{0} ^{1}

=4−23(1)=103=4-\frac{2}{3}(1)=\frac{10}{3} at α=1⇒f(1)\alpha=1 \Rightarrow \mathrm{f}(1)

x=0,x=1,y2=x\mathrm{x}=0, \mathrm{x}=1, \mathrm{y}^{2}=\mathrm{x},

y=∣x−5∣−∣1−x∣+x2\mathrm{y}=|\mathrm{x}-5|-|1-\mathrm{x}|+\mathrm{x}^{2} in x∈(0,1)\mathrm{x} \in(0,1)

y=5−x−(1−x)+x2\mathrm{y}=5-\mathrm{x}-(1-\mathrm{x})+\mathrm{x}^{2} y=4+x2\mathrm{y}=4+\mathrm{x}^{2}

A2=∫01((4+x2)−(x))dxA_{2}=\int_{0}^{1}\left(\left(4+x^{2}\right)-(\sqrt{x})\right) d x =4x+x33−x3232∣01=4 x+\frac{x^{3}}{3}-\left.\frac{x^{\frac{3}{2}}}{\frac{3}{2}}\right|_{0} ^{1}

=4+13−23=113=4+\frac{1}{3}-\frac{2}{3}=\frac{11}{3}

∣f(0)+f(1)∣=∣A1+A2∣=∣103+113∣=∣213∣=7|f(0)+f(1)|=\left|A_{1}+A_{2}\right|=\left|\frac{10}{3}+\frac{11}{3}\right|=\left|\frac{21}{3}\right|=7

figure

Solution figure

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Subject
Mathematics
Chapter
Area under the Curves
Topic
Area under the Curves