Question: http://goo.gl/yxQ1V 4B-2 (from 4B-1e)
Answer: http://goo.gl/

In the answer, how do we get from:
(continued in comments)

Question

Question: http://goo.gl/yxQ1V 4B-2 (from 4B-1e)
Answer: http://goo.gl/

In the answer, how do we get from:
(continued in comments)

anonymous · Answer

$$x^2-2x+y=0$$
to
$$x=1+-\sqrt{1-y}$$

hartnn · Answer

u know quadratic formula ?

anonymous · Answer

yeah i know

anonymous · Answer

i figured this was derived from the quadratic formula

hartnn · Answer

yes,
Compare your quadratic equation with $ax^2+bx+c=0$
find a,b,c
then the two roots of x are:
 $\huge{x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}}$

anonymous · Answer

yeah thats how i approached this too, but what i couldn't quite grasp logically is why we use constants for b and a, while we use the variable y for c (while x is left out)

hba · Answer

Yeah Thats How It Goes

hartnn · Answer

u mean why is y treated as constant ?

anonymous · Answer

yesh

hartnn · Answer

i cannot open your answer... i thonk since we are rotating around y axis, y remains constant, but not sure

hartnn · Answer

*think

anonymous · Answer

oh sorry, reposting answer @hartnn http://goo.gl/kFyIq

anonymous · Answer

but i think you got it right there without even seeing the answer @hartnn

anonymous · Answer

that explanation makes intuitive sense

hartnn · Answer

yeah, i would reply same after going through solution

anonymous · Answer

Alright thanks for your time once again :)

hartnn · Answer

welcome ^_^