F.5 Maths equation of circle

In the first place, please do INTERGRATE the maths concept and don't just memorize and recite the maths theorem (base angles, isos. triangles, etc.) and you cant get at least lv 5 in DSE gaa, I'm sure you want it, right??

1.
Q:Why in the calculation the book does not say that x is not equal to -5 and 2?
A:Actually if x is not equal to-5 or 2,angle AEB = 90 degree, so 2 expressions are actually the same. If x = -5 or 2, point E will lie on the diameter AB, which becomes point A or point B, thus ABE is collinear( in the same line) so the angle AEB will become 180 degrees.

2.
Q:Why we can use this method to find the equation of circle?
A:If AB is an diameter, a point in the circle, mark it as point E (except position of A &B) will make a right angle with A & B, you remember what's angle in semi-circle in Ch.10????so slope of AE times slope of BE =-1, since they are perpendicular, and then solve it using the coordinates of A,B and E (x,y)

dse仲有391日 lol
be fd ok? xppp
sorry for my goodest english lol

其實 first picture 第1行 "Let ... excluding A and B"

This is not directly related, but I find it interesting.

http://andrew-euclid.blogspot.com/2014/06/level-12-find-center-of-circle.html

If not exclude, then it becomes an imaginary circle, i.e. radius = 0
It is a line, not a circle