Published by:
CGP EDU Academic Team
Published on: August 13, 2026
The coefficient of x 7 in the expansion of (1 – x – x 2 + x 3 ) 6 is :
Text Solution
Verified by ExpertsThe correct answer is:
C
(1 – x – x 2 + x 3 ) 6
(1 – x) 6 (1 – x 2 ) 6
( 6 C 0 – 6 C 1 x 1 + 6 C 2 x 2 – 6 C 3 x 3 + 6 C 4 x 4 – 6 C 5 x 5 + 6 C 6 x 6 ) ( 6 C 0 – 6 C 1 x 2 + 6 C 2 x 4 – 6 C 3 x 6 + 6 C 4 x 8 +............+ 6 C 6 x 12 )
Now coefficient of x 7 = 6 C 16 C 3 – 6 C 36 C 2 + 6 C 56 C 1
= 6 × 20 – 20 × 15 + 36
= 120 – 300 + 36
= 156 – 300 = – 144
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