Mathematics · Binomial Theorem

JEE Main 2025 — 2 April, Morning Shift — Question 28

The term independent of xx in the expansion of ((x+1)(x2/3+1−x1/3)−(x−1)(x−x1/2))10,x>1\left(\frac{(x+1)}{\left(x^{2 / 3}+1-x^{1 / 3}\right)}-\frac{(x-1)}{\left(x-x^{1 / 2}\right)}\right)^{10}, x>1, is:

  1. Option A:

    120120

  2. Option B:

    240240

  3. Option C:

    210210

    Correct
  4. Option D:

    150150

Answer: C

Step-by-step solution

(x+1)=[(x1/3)+1][x2/3−x1/3+1](x+1)=\left[\left(x^{1 / 3}\right)+1\right]\left[x^{2 / 3}-x^{1 / 3}+1\right]

(x+1)=(x−1)(x+1)(x+1)=(\sqrt{x}-1)(\sqrt{x}+1)

Now,

(x+1x2/3−x1/3+1)=(x1/3+1)\left(\frac{x+1}{x^{2 / 3}-x^{1 / 3}+1}\right)=\left(x^{1 / 3}+1\right)

x−1x−x1/2=(x−1)(x+1)(x)2−x\frac{x-1}{x-x^{1 / 2}}=\frac{(\sqrt{x}-1)(\sqrt{x}+1)}{(\sqrt{x})^{2}-\sqrt{x}}

[(x1/3+1)−(1+1x)]10=[x1/3−1x1/2]10\left[\left(x^{1 / 3}+1\right)-\left(1+\frac{1}{\sqrt{x}}\right)\right]^{10}=\left[x^{1 / 3}-\frac{1}{x^{1 / 2}}\right]^{10}

Tr+1=10Cr[−1x1/2]r⋅(x1/3)10−rT_{r+1}={ }^{10} C_{r}\left[-\frac{1}{x^{1 / 2}}\right]^{r} \cdot\left(x^{1 / 3}\right)^{10-r}

⇒x(10−r3−r2)⋅10Cr(−1)r\Rightarrow \quad x^{\left(\frac{10-r}{3}-\frac{r}{2}\right)} \cdot{ }^{10} C_{r}(-1)^{r}

The term independent of xx when exponent of xx is 0 .

⇒r=4\Rightarrow r=4

So, term →10C4(−1)4x0=210\rightarrow{ }^{10} C_{4}(-1)^{4} x^{0}=210

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Subject
Mathematics
Chapter
Binomial Theorem
Topic
Binomial Coefficients
The term independent of x in the expansion of (frac (x+1) (x 2 / 3… | JEE Main 2025 PYQ with Solution · DhiX AI