q⁡t-f⁡t=ⅇσ⁢t2⁢π⁢limη→∞⁡∫-ηηⅇⅈ⁢t⁢τ⁢Q⁡σ+ⅈ⁢τ-F⁡σ+ⅈ⁢τ⁢ⅆ⁡τ.