互为相反数则相加为0x-(x-1)\3+(x+3)\5-7=0两边乘1515x-5x+5+3x+9-105=015x-5x+3x=105-5-913x=91x=91÷13x=7
x-(x-1)\3=-(x+3)\5+7，解得x=109\13
