Question

已知（3x的平方减2x加1）乘（x加b)的乘积中不含x的平方项，求b的值 如何做

认真点

Answer 1

(3x²-2x+1)(x+b)
=3x³+(3b-2)x²+(1-2b)x+b
不含x²则它的系数为0
3b-2=0
b=2/3

Answer 2

f(x+t)=sin(x/2+t/2+π/3)=cos(x/2)
cos[π/2-(x/2+t/2+π/3)]=cosx/2
cos(-x/2-t/2+π/6)=cosx/2
cos(x/2+t/2-π/6)=cosx/2
所以t/2-π/6=0
t=π/3