已知-3已知-3已知-3抱歉!原题打字有误,应该是“lm-2l+lm+3l-l3m+9l”吧lm-2l+lm+3l-l3m+9l=(2-m)+(m+3)-(3m+9)=-3m-4
已知-3抱歉!原题打字有误,应该是“lm-2l+lm+3l-l3m+9l”吧lm-2l+lm+3l-l3m+9l=(2-m)+(m+3)-(3m+9)=-3m-4