Formula ∫ 0 x [ ∫ 0 u φ ( t ) d t ] d u = ∫ 0 x [ ∫ t x φ ( t ) d u ] d t \int_0^x \left[ \int_0^u \varphi(t)dt\right] du = \int_0^x \left[ \int_t^x \varphi(t)du\right] dt ∫0x[∫0uφ(t