分析:(1)首先把整式進(jìn)行化簡(jiǎn),化簡(jiǎn)時(shí)要注意去括號(hào)時(shí),括號(hào)前面是負(fù)號(hào),去掉括號(hào)和負(fù)號(hào)后要把括號(hào)里的各項(xiàng)都變號(hào),然后再合并同類項(xiàng),把m和n的值代入求出結(jié)果.
(2)首先利用乘法分配律把整式進(jìn)行化簡(jiǎn),化簡(jiǎn)后再代入未知數(shù)x的值,即可得到答案.
解答:(1)解:(4m-n)-[1-(m+4n)],
=4m-n-(1-m-4n),
=4m-n-1+m+4n,
=5m+3n-1,
當(dāng)m=
,n=
1時(shí),
原式=
5×+3×1-1=2+4-1=5.
(2)解:
6×(-),
=
6×-6×,
=3(x-1)-4,
=3x-3-4=3x-7,
當(dāng)x=2時(shí),原式=3x-7=3×2-7=-1.
點(diǎn)評(píng):此題主要考查了整整式的化簡(jiǎn)求值問(wèn)題,必須根據(jù)要求首先化簡(jiǎn)再代入求值,化簡(jiǎn)過(guò)程中一定要認(rèn)真仔細(xì).