Your factors must begin 3x and x to give 3x2. The factors of 12 are 1/12, 2/6 and 3/4. Which pair, together with 3x and x, can add to -5? 3 and 4 seem to fit the bill:
(3x + 4)(x - 3)
It is: (3x+4)(2x-3) when factored
3x2-x-2 = (3x+2)(x-1)
It is: (2x+3)(3x-8) when factored
20x2 - 3x + 10 does not have any real factors.
(18x^(2) - 3x) '3x' is a common factor to both terms , so 'take it out'. Hence 3x(6x - 1) Fully factored.
3x squared minus 25x minus 28
x(3x - 2)
(x-3)(3x+1)
(3x + 1)(x - 5)
(3x + 8)(3x - 8)
It is: (3x+4)(2x-3) when factored
3x2-x-2 = (3x+2)(x-1)
(x + 2)(3x - 1)(3x + 1)
It is: (2x+3)(3x-8) when factored
3x^2 -14x +15 = (3x-5)(x-3)
20x2 - 3x + 10 does not have any real factors.
What is the question? Do you want to factor 3x2 -x -2? If that is the question the answer is (3x + 2)(x-1)