Perhaps you want to factor these.
The first one cannot be factored as written. A different expression can be.
.. q^2 +11qt +18t^2 = (q^2 +9qt) +(2qt +18t^2) = q(q +9t) +2t(q +9t)
.. = (q +2t)*(q +9t)
x^2 -14xy -15y^2 = (x -15y)*(x +y) . . . . . . . -15 and 1 are factors of -15 that add to -14