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If "b^2 - 4ac" is a perfect positive square there will be factors.
Use that as a test before trying to factor.
Here is an example of how to split the middle term to find those factors.
10x^2 + 7x - 12 = 5x*2x + 15x - 8x - 4*3
= 5x*2x + 5x*3 - 4*2x - 4*3
= 5x(2x + 3) - 4(2x + 3) = (5x - 4)(2x + 3)
9x^2 - 56x + 6
= 9x^2 - 2x - 54x - 6*(-2)
= x*9x - x*2 - 6*9x - 6*(-2)
= x(9x - 2) - 6(9x - 2)
you finish that one off.
Over to you now for the others