We know that,
p(x)=a0+a1x+⋯+anxn⇒p′(x)=a1+2a2x+⋯nanxn−1⇒p′(1)=a1+2a2+⋯+nan
As,
|p(x)|≤|ex−1−1|⇒|p(1)|≤0⇒p(1)=0|p(h+1)|≤|eh−1| ∀h≥−1⇒|p(h+1)−p(1)|≤|eh−1|⇒∣∣∣p(h+1)−p(1)h∣∣∣≤∣∣∣eh−1h∣∣∣
Taking limit h→0
limh→0∣∣∣p(h+1)−p(1)h∣∣∣≤limh→0∣∣∣eh−1h∣∣∣⇒|p′(1)|≤1
Hence
|a1+2a2+⋯+nan|≤1