not: the divide sign (÷) becomes (*) and (a+1)/(a²-8a+15) becomes (a²-8a+15)/(a+1)
The original divisor of {(a+2)/(a-5) ÷ (a+1)/(a²-8a+15)} = [(a+2)/(a-5)] * [(a-3) (a-5)/(a+1)] If a = 1 or a = 5 that expression would be undefined, so we will restrict those values