æ ¹æ®æ±æ ¹å
¬å¼,Xa=(-b+â(b^2-4ac))/2a
Cç¹(0,c)
0A=|Xa|=(b-â(b^2-4ac))/2a
OC=|Yc|=c
OA=OC -> (b-â(b^2-4ac))/2a=c -> b-2ac=â(b^2-4ac) -> (b-2ac)^2=b^2-4ac ->
b^2-4abc+4a^2c^2=b^2-4ac -> a^2c^2+ac=abc -> ac+1=b
æ
éA
追é®æçä¸æ符å·ï¼è½ä¸ç¨ç»å¾å·¥å
·ï¼è°¢è°¢