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JEE Mains · Maths · STD 11 - 7. binomial theoram

If in the expansion of \((1+x)^{\mathrm{p}}(1-x)^{\mathrm{q}}\), the coefficients of \(x\) and \(x^2\) are 1 and -2 , respectively, then \(\mathrm{p}^2+\mathrm{q}^2\) is equal to :

  1. A 18
  2. B 13
  3. C 8
  4. D 20
Verified Solution

Answer & Solution

Correct Answer

(B) 13

Step-by-step Solution

Detailed explanation

(1+\mathrm{x})^{\mathrm{p}}(1-\mathrm{x})^{\mathrm{q}}=\left({ }^{\mathrm{p}} \mathrm{C}_0+{ }^{\mathrm{p}} \mathrm{C}_1 \mathrm{x}+{ }^{\mathrm{p}} \mathrm{C}_2 \mathrm{x}^2+\ldots\right)\left({ }^{\mathrm{q}} \mathrm{C}_0-{ }^{\mathrm{q}} \mathrm{C}_1 \mathrm{x}+{…