题目

用简便方法计算：( )×(-24) 答案：解：原式=( −16 )×(-24)+ 512 ×(-24)- 78 ×(-24) =15．20．解三元一次方程组：$\left\{\begin{array}{l}{2x+y+z=15}\\{x+2y+z=16}\\{x+y+2z=17}\end{array}\right.$．