-b/2a= 1/2 ①
4a+2b-c=4 ②
∫x 12+x22 = 13 is equivalent to (x1+x2) 2-2x1x2 =13.
According to Vieta's theorem.
(-b/a)2-2c/a= 13 ③
Simultaneous solution of three equations
a= - 1 b= 1 c= - 6
∴y= - x2+x+6
(2) calculate B C according to the equation.
They are (3,0) (-2,0).
S△ABC= 10
Then S△PBC=5.
BC = 5
When p is on a straight line with y =±2, all meet this requirement.