∫45dx + 6∫12dx
\(\begin{array}{rcll} \int {54\ dx} + 6\cdot \int {12\ dx} &=& 54\cdot \int {dx} + 6\cdot12\cdot \int {dx} \\ &=& 54\cdot x + 6\cdot12\cdot x\\ &=& 54\cdot x + 72\cdot x\\ &=& 126\cdot x\\ \end{array}\)
