Let (1 + 2x + x^2)^4 = a_0 + a_1 x + a_2 x^2 + ... + a_8 x^8. What is the value of a_1 + a_3 + a_5 + a_7?
(x^2 + 2x + 1)^4 =
[ ( x + 1)^2 ] ^4 =
(x + 1)^8 = 1 x^8 + 8x^7 + 28x^6 + 56x^5 + 70x^4 + 56x^3 + 28x^2 + 8x + 1
a1 = 8
a3 = 56
a5 = 56
a7 = 8
Sum = 64 * 2 = 128
