(1) 4x^{2}-28x-72
Step 1: Factor 4 out of the equation
4(x^{2}-7-18)
Step 2: Find two numbers that multiply to get -18 and add to get -7
4(x-9)(x+2)
(2) -x^{2}+8x-15
Step 1: Factor -1 out of the equation
-1(x^{2}-8x+15)
Following the same steps from #1:
-1(x-3)(x-5)