About Session 9, Clip 3 on product rule.
At about 6 min. 8 sec into the video, the professor says that he introduced u(v(x+∆x) which he didn't like. However, the formula until then reads (u(x+∆x)-u(x))v(x+∆x), so the u in u(v(x+∆x) doesn't concern v(x+∆x) but belongs to (u(x+∆x)-u(x)) as is indicated by the brackets.

He later introduced +u(x)v(x+∆x) to cancel for something that actually was not there in the first place.
Although it ends up as it should, I cannot follow the explantion provided. The explanation in the lecture notes seems more logical.
Did I miss something?

Question

About Session 9, Clip 3 on product rule.
At about 6 min. 8 sec into the video, the professor says that he introduced u(v(x+∆x) which he didn't like. However, the formula until then reads (u(x+∆x)-u(x))v(x+∆x), so the u in u(v(x+∆x) doesn't concern v(x+∆x) but belongs to (u(x+∆x)-u(x)) as  is indicated by the brackets.

He later introduced +u(x)v(x+∆x) to cancel for something that actually was not there in the first place. 
Although it ends up as it should, I cannot follow the explantion provided. The explanation in the lecture notes seems more logical.
Did I miss something?

stacey · Answer

Can you give a website address?

anonymous · Answer

Dear Stacey, Sorry it took a few days. The address is http://ocw.mit.edu/courses/mathematics/18-01sc-single-variable-calculus-fall-2010/part-a-definition-and-basic-rules/session-9-product-rule/ from the course 18-01sc single variable calculus with kind regards Frank