Algebraic long division:
2x + 3
3x+5 ) 6x2+19x +7
- (6x2+10x)
9x +7
- (9x+15)
-8
Quotient is 2x+3. remainder -8. (2x+3)(3x+5)-8=6x2+19x+7
Synthetic division (divide by factor -5/3):
-5/3 | 6 19 | 7
6 -10 | -15
6 9 | -8 = 6x+9, remainder -8
Quotient is 6x+9, remainder -8.
(6x+9)(x+5/3)-8=(2x+3)(3x+5)-8 explains the apparent discrepancy between the two methods.