A function f(x) satisfies f(1)=−3,f ′ (1)=1;f ′′ (1)=−1,f′′(1)=−1, What is the coefficient c₂​ in the Taylor series expansion of f(x) c₀ +c₁ (x−1)+c₂​ (x−1)² +c₃ (x−1)³ +⋯?