文科的学习

BigPaul

锦衣卫:

一直欣赏乡下人对小孩学习的深入了解和课外辅导,令老锦近来也关心起家中读初中三的小儿子的功课,甚至唬住孩子说,老锦的数学由小学到大学都很好,什么难题问我都行.

今天,小儿拿着一本数学作业书过来,非常虚心地指着作业书中的题目,问老锦如何解答,老锦当然义不容辞啦. 谁知一看题目,个头马上大起来, 题目问: Why (a+b)+(-a) = (b+a)+(-a) ? 中文是:为什么 (a+b)+(-a) = (b+a)+(-a) ? 换而言之,题目是在问: Why (a+b) = (b+a) ? 即是问 为什么 (羊 + 狗) 等于 (狗 + 羊) ? 老锦翻来復去弄了半天也都答不出为什么 (羊 + 狗) 等于 (狗 + 羊) ? 只好放上网上,借用乡下人的帖子,请乡下人或知者提供个正确答案,好让孩儿完成功课.谢谢!

［此帖子已被 锦衣卫 在 2009-1-6 13:11:44 编辑过］

a+b=b+a is true because of the

Commutative Property of Addition.

加法的交換律

乡下人

锦衣卫:

一直欣赏乡下人对小孩学习的深入了解和课外辅导,令老锦近来也关心起家中读初中三的小儿子的功课,甚至唬住孩子说,老锦的数学由小学到大学都很好,什么难题问我都行.

今天,小儿拿着一本数学作业书过来,非常虚心地指着作业书中的题目,问老锦如何解答,老锦当然义不容辞啦. 谁知一看题目,个头马上大起来, 题目问: Why (a+b)+(-a) = (b+a)+(-a) ? 中文是:为什么 (a+b)+(-a) = (b+a)+(-a) ? 换而言之,题目是在问: Why (a+b) = (b+a) ? 即是问 为什么 (羊 + 狗) 等于 (狗 + 羊) ? 老锦翻来復去弄了半天也都答不出为什么 (羊 + 狗) 等于 (狗 + 羊) ? 只好放上网上,借用乡下人的帖子,请乡下人或知者提供个正确答案,好让孩儿完成功课.谢谢!

［此帖子已被 锦衣卫 在 2009-1-6 13:11:44 编辑过］

老锦真是大材小用,小题大做.你提到的数是Algebra 1 ,即代数1,在美国为第八年级数学课,(初二).叫Associative(联合数),在括号内的a和b都是正数,而且a和b在式中是相加,因此a和b可以相互挽位而不会改变其结果.

锦衣卫

多谢绿草,ssh, BigPaul和乡下人的帮助,小儿采纳了ssh的答案,就是BigPaul 所说的\"加法的交換定律\".

人到了一定的年纪,习惯了一些必然的规则和定律,有时也就只知其然,而忘记了其所以然,即是说,反正見到三伯就叫\"伯川\"冇错了,但是怎解呢?原来三伯是被人冠以\"伯川\"之名,亦即是说,三伯是伯川的原因就是人为的称呼交换定律.

BigPaul

SSH's right on! SSH must be a math teacher. It's hard to come up with the exact name! BTW, my 7-grader at home also get it right.

ssh

BigPaul:

SSH's right on! SSH must be a math teacher. It's hard to come up with the exact name! BTW, my 7-grader at home also get it right.

BigPaul,

Your son must be very smart. Congratulations!

I am not a math teacher. I worked with my son on some math problems a couple of years ago when he was in middle school, so these basic concepts are still fairly fresh in my mind.

I wouldn't mind becoming a math teacher as a second career though. My son had a Social Studies teacher who took early retirement, when she was still in her early 50's, from a senior executive position with a major telecommunications firm to become a teacher. Though still not common, an increasing number of these highly compensated executives and professionals are quitting the rat race that is Corporate America. I hope to be able to do the same some day.

［此帖子已被 ssh 在 2009-1-8 14:25:00 编辑过］

远游客

这个题目有点意思。既然是文科学习,就来点文科交流,对话练习。