The sum of the coefficients of the polynomial obtained by collection of the like terms after the expansion above is?
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The function f ( x ) can be expanded into a polynomial with integer coefficients a n as follows:
f ( x ) = ( 1 − 2 x + 2 x 2 ) 7 4 3 ( 2 + 3 x − 4 x 2 ) 7 4 4 = a 2 9 7 4 x 2 9 7 4 + a 2 9 7 3 x 2 9 7 3 + a 2 9 7 2 x 2 9 7 2 + . . . + a 2 x 2 + a 1 x + a 0
We note that f ( 1 ) gives us the sum of the coefficients.
f ( 1 ) = a 2 9 7 4 + a 2 9 7 3 + a 2 9 7 2 + . . . + a 2 + a 1 + a 0 = ( 1 − 2 + 2 ) 7 4 3 ( 2 + 3 − 4 ) 7 4 4 = 1