Test:351 QNo:38

Q38 The sum of the coefficients of the polynomial (1-x-x2)313
a) 0
b) -1
c) 1
d) can't be determined
Your Answer: (a)
Correct Answer: (b)
Score: -1
Explaination :
it can be obtained by putting x=1 in the expression

(-1)313=-1

what is the basic way to do this 1 ??

y can't we put x=-1??????

yeah rite answer is -1

we always put x=1

kyun............papa ko pooch :P

i am not in the mood to joke

please can anybody help in his 1??

it is because every general term will be of the form

C_kx^k where C is its coefficient

when you put x=1 we have the sum as ΣC_k which gives the sum of coefficients

but putting x=-1 will give it as -C1+C2 ... which is not the sum