表示否定的前缀ir, un, im, non, dis等的添加规律 表示否定的前缀  im-加在字母m,b,p之前  impossible（不顺能的），impolite（不礼貌的），impudence（厚颜无耻）  in-加在形容词，名词之前  incorrect（不正确的），inability（无能，无力），inaccurate（不准确的）  ir-加在以r开头的词前  irregular（不稳定的），irresistable（不可抵抗的），irresolvable（不能分解的，不能解决的）  un-加在名词，形容词，副词之前  unfinished（未完成的）undoubted（无疑的）unemployment（失业）  语法易错题 速记英语单词的方法 高中英语教材 还有一些前缀的规则： non-加在形容词，名词前  non-existence（不存在），non-essential（不主要的），non-electrical（非电的）  mis－加在动词、名词之前  misunderstand（误解），misjudge（误判），misleading（误导），misfortune（不幸）  dis-加地动词之前  disappear（消失），disarm（解除武装），disconnect（失去联系）  de-加在名词，形容词之前  demobilize(遣散；使…复员) decolor (脱色, 漂白)  anti-加在名词、形容词之前  anti-Japanese（抗日战争），anti-social（厌恶社会的，反社会的），antidite（解毒药）  counter-加在名词、动词前  counterattack（反攻，反击），counteract（抵抗，阻碍）counterrevolution（反革命）      A talented speaker who was always able to connect with his audience, Reagan became involved in politics in the 1950s. This popular touch led to him being elected the governor of California in 1967.     All the while Reagan was in California, he had his eye on the White House. In 1980, aged 69, he became the oldest man ever elected president.     He held office from 1981 to 1989, the first president to serve two complete terms after World War Ⅱ. When he left, aged 77, he held the highest popularity rate of any retiring president in US history.     He remained positive even when he discovered he had an illness that would destroy him. “I will leave with the greatest love for this country of ours and eternal（永恒的） optimism for its future,” he wrote.