The equation can be factorized by inspection. The two numbers in the brackets must multiply together to make -165, so.....
If you find all the prime factors of 165, they are 3, 5, and 11. and note that 3x5 = 15
You also know that the sum of the two numbers in the brackets must be -4.
x^2-4x-165 = (x+11)(x-15)