
Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class
Examples
Example 2 Important
Example 3 Important
Example 4
Question 1 Important Deleted for CBSE Board 2024 Exams
Question 2 Important Deleted for CBSE Board 2024 Exams
Question 3 Deleted for CBSE Board 2024 Exams You are here
Question 4 Important Deleted for CBSE Board 2024 Exams
Question 5 Deleted for CBSE Board 2024 Exams
Question 6 Important Deleted for CBSE Board 2024 Exams
Question 7 Important Deleted for CBSE Board 2024 Exams
Question 8 Deleted for CBSE Board 2024 Exams
Question 9 Important Deleted for CBSE Board 2024 Exams
Question 10 Important Deleted for CBSE Board 2024 Exams
Question 11 Important Deleted for CBSE Board 2024 Exams
Question 12 Deleted for CBSE Board 2024 Exams
Question 13 Important Deleted for CBSE Board 2024 Exams
Last updated at May 29, 2023 by Teachoo
Question 3 Find the coefficient of x6y3 in the expansion of (x + 2y)9. We know that General term of expansion (a + b)n is Tr+1 = nCr an–r br For (x + 2y)9, Putting n = 9 , a = x , b = 2y Tr + 1 = 9Cr (x)9 – r (2y)r = 9Cr (x)9 – r . (y)r . (2)r We need to find coefficient of x6 y3 Comparing yr = y3 r = 3 Putting r = 3 in (1) T3+1 = 9C3 x9 – 3 . y3 . (2)3 = 9!/3!(9 −3 )! x6 . y3 . (2)3 = 9!/(3! 6!) (2)3 x6 y3 = (9 × 8 × 7 × 6!)/(3 × 2 × 1 × 6!) × 8 . x6 y3 = (9 × 8 × 7 × 8 )/(3 × 2) x6 y3 = 672 x6 y3 Hence coefficient of x6 y3 is 672