Question

The coefficient of x7 in the expansion of (1 - x - x2 + x3)6 is :-
(1) - 144
(2) 132
(3) 144
I
jan s. 20​

Answer 1

Answer:

(1 - x - x2 + x3)6

= (1 - x)6(1 - x2)6

= (6C0 - 6C1 x + ... + 6C6 x6)(6C0 - 6C1 x2 + ... + 6C6 x12)

Now, coefficient of x7 is  = 6C1 6C3 - 6C3 6C2+ 6C5 6C1

Step-by-step explanation: