由题意,知
M≥|f(1)|=|1+p+q|,
M≥|f(-1)|=|1-p+q|,
M≥|f(0)|=|q|=|-q|.
即4M≥|1+p+q|+2|-q|+|1-p+q|
≥|1+p+q-2q+1-p+q|
=2
故M≥1/2.
而当f(x)=x^2-1/2时,M=1/2.
∴M|min=1/2.