Substituting x=-4 and y=0 gives: -4k+3=0,
∴k=3/4，
The analytical formula of the straight line is: y=3/4x+3,
② It is known that the coordinate of point P is (1, m),
∴m=3/4× 1+3= 15/4；
(2)∫PP '∨AC，
△PP'D∽△ACD，
∴P'D/DC=P'P/CA, that is, 2a/(a+4)= 1/3.
∴a=4/5；
(3) The following discussion is divided into three situations.
(1) When the point p is in the first quadrant,
1) If ∠ AP 'c = 90, P 'a = P 'c, (as shown in figure 1).
Passing point p' is the axis of P'H⊥x at point H.
∴PP'=CH=AH=P'H= 1/2AC，
∴2a=( 1/2)(a+4)，
∴a=4/3，
∫P ' h = PC = 1/2AC，△ACP∽△AOB，
∴OB/OA=PC/AC= 1, that is, b/4= 1/2,
∴b=2.
2) If ∠ p 'ac = 90 and P'A=CA,
Then PP''=AC,
∴2a=a+4，
∴a=4，
∫P ' a = PC = AC，△ACP∽△AOB，
∴UB/OA=PC/AC= 1, that is, b/4= 1,
∴b=4.
3) If ∠ p 'ca = 90,
Then points p' and p are in the first quadrant, which contradicts the condition.
∴△P'CA can't be an isosceles right triangle with C as the right vertex.
② When point P is in the second quadrant, ∠P'CA is obtuse (as shown in Figure 3), at this time △P'CA cannot be an isosceles right triangle;
③ When p is in the third quadrant, ∠P'CA is an obtuse angle (as shown in Figure 4), at this time △P'CA cannot be an isosceles right triangle.
∴ All the values of A and B that meet the conditions are A = 4/3 and B = 2.
Or a = 4 and b = 4.