For example here: running-at-their-respective-constant-rates-machine-x-takes-98599.html
I don't really get how can one quickly
If a=1 it is easy a1*a2=c, a1+a2=-b, but what if a=/=1?
When I do quadratics, I always focus on the "c" portion, in this case the 24. This is helpful because you do not have to even consider the "a", or in this case the 5. Start with the factor pairs for 24 (12,2) (3,8) (4,6). Now think about which, of these three pairs, produces a -34 if you multiply one term by 5 and add it to the other? Also because 24 is (+), both factors need to be either positive or negative. In this case, both will be negative because of -34.
Start with (12,2): hmmm... [-12*5] + -2? No that doesn't give us -34. What about -12 + [-2*5]? No that doesn't give us -34 either
What about (4,6)? Oh look, -4+[-6*5] gives us -34! Therefore -4 and -6 must be our factor pair
MGMAT1 - 650 (Q44, V35)
MGMAT2 - 670 (Q42, V39)
MGMAT3 - 640 (Q44, V34)
MGMAT4 - 630 (Q41, V35)
GMATPrep1 - 720 (Q48, V40)
GMATPrep2 - 720 (Q48, V41)
MGMAT5 - 690 (Q45, V39)
GMATPrep3 - 700 (Q47, V39)
GMATPrep4 - 710 (Q49, V38) Got one less question wrong than on my V41, but for some reason got a V38!
Goal: 740 (Q49, V42)