Question

(x+1)^3=ax^3+bx^2+cx+d,求a+b+c+d的值

Answer 1

(x+1)^3=ax^3+bx^2+cx+d

=x^3+3x^2+3x+d

所以

a=1

b=3

c=3

d=1

所以a+b+c+d=8

或者取x=1

ax^3+bx^2+cx+d=a+b+c+d=(x+1)^3=(1+1)^3=8