You take out the common factor, namely, "g".
X squared + 7X + 12?
t(t-1)
13X squared + 7X + 12
What about it? Factorise it?
m(m - 1)
It is: x(x-3) factorized
x2 - 41 cannot be factorised.
x(x-7)
It is: 3y(2y-3x) when factored
x(x - 7)
7x-x2 = x(7-x)
x2 + 4x = x(x + 4)