I have been learning how to factor trinomials and I am stuck..
2x^2+x-15 = (2x-5)(x+3)
3a^2-2a-5 = (3a-5)(a+1)
Fc^2+17c+14 = (fc+7)(c+2)
To factor these types of problems, is the only way real to just plug in factors and do a full test with foil?? I mean some of these could have 100 possible factor pairs.. do you have to plug them in and keep going until it works? Am I missing a shortcut?