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Maths Question 7 – JEE-MAIN 2026

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The coefficient of x2 in the expansion of (2x2+1x)10, x≠0, is :

Recall the general term formula for a binomial expansion (a+b)n.

● Video Walkthrough
Step 1: Identify the General Term✦ Active

The general term Tr+1 in the binomial expansion of (a+b)n is given by Tr+1=(nr)an−rbr. For the given expression (2x2+1x)10, we have a=2x2, b=x−1, and n=10. Substituting these values, the general term is:

Tr+1=(10r)(2x2)10−r(x−1)r
Step 2: Determine the Value of r○ Expand

Simplify the general term to find the power of x:

Tr+1=(10r)210−r(x2)10−rx−r=(10r)210−rx2(10−r)x−r=(10r)210−rx20−2r−r=(10r)210−rx20−3r

We need the coefficient of x2, so we equate the power of x to 2:

20−3r=2⟹3r=18⟹r=6
💡 Teacher's Secret Hint

Ensure careful handling of exponents when combining terms with x.

Step 3: Calculate the Coefficient○ Expand

Substitute r=6 into the coefficient part of the general term:

Coefficient=(106)210−6=(106)24

Calculate the binomial coefficient and the power of 2:

(106)=(104)=10×9×8×74×3×2×1=10×3×7=210
24=16

Multiply these values to get the final coefficient:

Coefficient=210×16=3360
💡 Teacher's Secret Hint

Remember that (nk)=(nn−k) can simplify calculations.

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