Question 839487
Part (a) appears to be the only troubling one.


Try this:
{{{(2a+- what)(a+- whatelse)}}}
You want to find combinations of "what" and "whatelse" which will give product of -3 and after doing the binomial multiplications gives sum of -5.


Try 1, -3:
{{{(2a+1)(a-3)}}}---<--------This is the answer, factored.
{{{2a^2+a-6a-3}}}
{{{highlight_green(2a^2-5a-3)}}} ----- the given expression to be factored.
GOOD.  This one works.
Answer:  {{{highlight((2a+1)(a-3))}}}



What happens if you tried the other combinations...


Try -1, 3:
(2a-1)(a+3)
2a^2-1a+6a-3
2a^2+5a-3
No good.


Try 3, -1:
(2a+3)(a-1)
2a^2+3a-2a-3
2a^2+a-3
No good.


Try -3, 1:
(2a-3)(a+1)
2a^2-3a+2a-3
2a^2-a-3